Due to federal budget cuts, Federal Aviation officials say furloughs are taking effect Sunday and that could mean delays for local airline travelers.

The Transportation Security Administration will have the National Academy of Sciences study the health effects of X-ray body scanners used in airports. (David McNew/Getty Images)

(Michael Grabell ProPublica) Following months of congressional pressure, the Transportation Security Administration has agreed to contract with the National Academy of Sciences to study the health effects of the agency's X-ray body scanners. But it is unclear if the academy will conduct its own tests of the scanners or merely review previous studies.

The machines, known as backscatters, were installed in airports nationwide after the failed underwear bombing on Christmas Day 2009 to screen passengers for explosives and other nonmetallic weapons. But they have been criticized by some prominent scientists because they expose the public to a small amount of ionizing radiation, a form of energy that can cause cancer.

The scanners were the subject of a 2011 ProPublica series, which found that the TSA had glossed over the small cancer risk posed by even low doses of radiation. The stories also showed that the United States was almost alone in the world in X-raying passengers and that the Food and Drug Administration had gone against its own advisory panel, which recommended the agency set a federal safety standard for security X-rays.

The TSA maintains that the backscatters are safe and that they emit a low dose of X-rays equivalent to the radiation a passenger would receive in two minutes of flying at typical cruising altitude.

Sen. Susan Collins of Maine, the top Republican on the Senate homeland security committee, introduced a bill mandating such a test earlier this year.

"I am pleased that at long last the Transportation Security Administration has heeded my call to commission an independent examination into the possible health risks travelers and TSA employees may face during airport screenings," she said in a statement Monday night.

According to a brief contract notice posted on a government procurement website, the National Academy of Sciences will convene a committee to review previous studies to determine if the dose from the scanners complies with existing health and safety standards and to evaluate the TSA's methods for testing and maintaining the machines.

Collins' office said the language in the contract notice wasn't final and that the study would be consistent with the senator's calls for an independent investigation. TSA spokesman David Castelveter added, "Administrator [John] Pistole has made a commitment to conduct the study and TSA is following through on that commitment."

Still, it's unclear how much the study that the TSA is proposing will add to what's known about the machines, mainly because it's not known if the National Academy of Sciences will conduct new tests or confine itself to examining previous studies. In the past, TSA has contracted with the Food and Drug Administration, the Johns Hopkins Applied Physics Laboratory and the Army Public Health Command to test the scanners. All three studies found the radiation was in line with a voluntary standard set by an industry panel that included FDA scientists.

A 2012 study by the Department of Homeland Security's independent watchdog supported the findings but based its report on previous tests performed by the TSA and the other groups.

This fall, the TSA began replacing the X-ray body scanners with millimeter-wave machines 2013 a technology radiation experts consider safer 2013 at most of its biggest airports. The TSA said the move was done to speed up lines and that the X-ray scanners would eventually be redeployed at smaller airports.

Here's a side-by-side comparison of the two types of scanners.

Europe has prohibited the X-ray scanners while Israel, which is influential in the security world, has recently begun testing them.

The TSA study will not address privacy, cultural or legal concerns that have been raised by the scans, the contract notice said.

A Transportation Security Administration volunteer demonstrates a full-body scanner at O'Hare International Airport on March 15, 2010 in Chicago. (Scott Olson/Getty Images)

(Michael Grabell, ProPublica) The Transportation Security Administration has been quietly removing its X-ray body scanners from major airports over the last few weeks and replacing them with machines that radiation experts believe are safer.

The TSA says it made the decision not because of safety concerns but to speed up checkpoints at busier airports. It means, though, that far fewer passengers will be exposed to radiation because the X-ray scanners are being moved to smaller airports.

The backscatters, as the X-ray scanners are known, were swapped out at Boston Logan International Airport in early October. Similar replacements have occurred at Los Angeles International Airport, Chicago O'Hare, Orlando and John F. Kennedy in New York, the TSA confirmed Thursday.

The X-ray scanners have faced a barrage of criticism since the TSA began rolling them out nationwide after the failed underwear bombing on Christmas Day 2009. One reason is that they emit a small dose of ionizing radiation, which at higher levels has been linked to cancer.

In addition, privacy advocates decried that the machines produce images, albeit heavily blurred, of passengers' naked bodies. Each image must be reviewed by a TSA officer, slowing security lines.

The replacement machines, known as millimeter-wave scanners, rely on low-energy radio waves similar to those used in cell phones. The machines detect potential threats automatically and quickly using a computer program. They display a generic cartoon image of a person's body, mitigating privacy concerns.

"They're not all being replaced," TSA spokesman David Castelveter said. "It's being done strategically. We are replacing some of the older equipment and taking them to smaller airports. That will be done over a period of time."

He said the TSA decided to move the X-ray machines to less-busy airports after conducting an analysis of processing time and staffing requirements at the airports where the scanners are installed.

The radiation risk and privacy concerns had no bearing on the decision, Castelveter said.

Asked about the changes, John Terrill, a spokesman for Rapiscan 2014 which makes the X-ray scanners 2014 wrote in an email, "No comment on this."

The TSA is not phasing out X-ray body scanners altogether. The backscatter machines are still used for screening at a few of America's largest 25 airports, but the TSA has not confirmed which ones. Last week, Gateway Airport in Mesa, Ariz., installed two of the machines.

Moreover, in late September, the TSA awarded three companies potential contracts worth up to $245 million for the next generation of body scanners 2014 and one of the systems, made by American Science & Engineering, uses backscatter X-ray technology.

The United States remains one of the only countries in the world to X-ray passengers for airport screening. The European Union prohibited the backscatters last year "in order not to risk jeopardizing citizens' health and safety," according to a statement at the time. The last scanners were removed from Manchester Airport in the United Kingdom last month.

Here's a side-by-side comparison of the two types of body scanners the TSA uses.

The X-ray scanner looks like two blue refrigerator-sized boxes. Unseen to the passenger, a thin beam scans left and right and up and down. The rays reflect back to the scanner, creating an image of the passenger's body and any objects hidden under his or her clothes.

The millimeter-wave scanner looks like a round glass booth. Two rotating antennas circle the passenger, emitting radio frequency waves. Instead of creating a picture of the passenger's body, a computer algorithm looks for anomalies and depicts them as yellow boxes on a cartoon image of the body.

According to many studies, including a new one conducted by the European Union, the radiation dose from the X-ray scanner is extremely small. It has been repeatedly measured to be less than the dose received from cosmic radiation during two minutes of the airplane flight.

Using those measurements, radiation experts have studied the cancer risk, with estimates ranging from six to 100 additional cancer cases among the 100 million people who fly every year. Many scientists say that is trivial, considering that those same 100 million people would develop 40 million cancers over the course of their lifetimes. And others, including the researchers who did the EU study, have said that so much is unknown about low levels of radiation that such estimates shouldn't be made.

Still, the potential risks have led some prominent scientists to argue that the TSA is unnecessarily endangering the public because it has an alternative 2014 the millimeter-wave machine 2014 which it also deems highly effective at finding explosives.

"Why would we want to put ourselves in this uncertain situation where potentially we're going to have some cancer cases?" David Brenner, director of Columbia University's Center for Radiological Research, told ProPublica last year. "It makes me think, really, why don't we use millimeter waves when we don't have so much uncertainty?"

Although there has been some doubt about the long-term safety of the type of radio frequency waves used in the millimeter-wave machines, scientists say that, in contrast to X-rays, such waves have no known mechanism to damage DNA and cause cancer.

The TSA has said that having both technologies encourages competition, leading to better detection capabilities at a lower cost.

But tests in Europe and Australia suggest the millimeter-wave machines have some drawbacks. They were found to have a high false-alarm rate, ranging from 23 percent to 54 percent when figures have been released. Even common things such as folds in clothing and sweat have triggered the alarm.

In contrast, Manchester Airport officials told ProPublica that the false-alarm rate for the backscatter was less than 5 percent.

No study comparing the two machines' effectiveness has been released. The TSA says its own results are classified.

Each week, the agency reports on various knives, powdered drugs and even an explosives detonator used for training that have been found by the body scanners.

But Department of Homeland Security investigators reported last year that they had "identified vulnerabilities" with both types of machines. And House transportation committee chairman John Mica, R-Fla., who has seen the results, has called the scanners "badly flawed."

According to the Department of Transportation: "The nation’s largest airlines set record marks during the first half of this year for on-time performance, the fewest long tarmac delays, and the lowest rates of canceled flights and mishandled baggage."

The press release goes on to say: "The 15 largest U.S. airlines posted an 83.7 percent on-time arrival rate during the first six months of 2012, the highest mark for any January-June period in the 18 years the Department has collected comparable data. The previous high was 82.8 percent in January-June 2003."

You can read the full report here.

Also this morning, a department within the DOT (the Bureau of Transportation Statistics) released data breaking out June's on-time numbers by airport. The upshot: you want to fly in or out of Salt Lake City, and avoid Newark. "Salt Lake City (90.59) had the highest and Newark (68.51) had the lowest on-time departure performance of the 29 busiest airports in June."

Other highlights:

• There was one international flight with tarmac time of more than four hours: Air Canada Flight 711 from New York LaGuardia to Toronto, which was on the LaGuardia tarmac on June 25 for 248 minutes before taking off.

• In June, the most delayed flights were: JetBlue Flight 24 from New York JFK to Syracuse and JetBlue Flight 23 from Syracuse to New York JFK. Both flights operated 10 times during the month and were 30 minutes late or canceled 80.0 percent of the time, averaging 81 minutes late.

You can see that data here.

Berlin Brandenburg Airport on May 4, 2012 (photo by Kate Hinds)

The opening of Europe's newest airport has been pushed back yet again, infuriating airlines, embarrassing local officials and complicating the start of the summer travel season.

Berlin Brandenburg Airport (BER) was to have begun welcoming traffic on June 3rd. An airport spokesperson even took a group of international reporters on a tour of the construction site last week, assuring the journalists -- who were outfitted in hardhats, boots and safety vests -- that everything was on track for an opening date that was just 30 days away.

That was then; this is now.

A statement on the airport's website reads "the planned inauguration of the airport on 3 June 2012 has become a race against time" and that problems with the airport's fire protection systems has  necessitated a postponement of the opening -- which "will commence operations after summer holiday period."

BER is designed to consolidate and expand air traffic from the city's two airports, Tegel and Schonenberg. On the evening of June 2nd, those two airports were to have closed to the public. Now they must remain open indefinitely -- and try to accommodate the flight schedule of carriers who were banking on BER.

The postponement is particularly vexing to Germany's two largest air carriers, which had been planning on the new airport to be open for the start of the summer travel season. The CEO of airberlin vented his frustration in an email to media.  “We have to work around the change of plan, which presents us with a huge challenge," said Hartmut Mehdorn. "It presents immense logistical problems for all involved and will also cause additional costs which have yet to be calculated.” Lufthansa -- the country's largest carrier -- had been planning to substantially increase the number of routes it offers in and out of Berlin. Airline officials said Tuesday they were scrambling to get additional landing slots at Tegel.

The postponement not only presents logistical challenges. The city is blanketed with signs advertising June 3rd as BER's opening date. As of May 7th, there were "Danke, Tegel" posters all over that airport, thanking it for years of service.

View a slideshow of photos taken of Berlin Brandenburg Airport on May 4, 2012, below. (All photos by Kate Hinds.)

The TSA testing new scanning technology at McCarrin Interational Airport in Las Vegas. (Photo by Ethan Miller/Getty Images)

(Michael Grabell, ProPublica) Sen. Susan Collins, the top Republican on the homeland security committee, plans to introduce a bill in the coming days that would require a new health study of the X-ray body scanners used to screen airline passengers nationwide.

The Transportation Security Administration began using the machines for routine screening in 2009 and sped up deployment after the so-called underwear bomber tried to blow up a plane on Christmas Day of that year.

But the X-ray scanners have caused concerns because they emit low levels of ionizing radiation, a form of energy that has been shown to damage DNA and mutate genes, potentially leading to cancer. ProPublica and PBS NewsHour reported in November that the TSA had glossed over cancer concerns. Studies suggested that six or 100 airline passengers each year could develop cancer from the machines.

Shortly after our report, the European Union separately announced that it would prohibit X-ray body scanners at its airports for the time being “in order not to risk jeopardizing citizens’ health and safety.”

The new bill drafted by Collins would require the TSA to choose an independent laboratory to measure the radiation emitted by a scanner currently in use at an airport checkpoint. The peer-reviewed study, to be submitted to Congress, would also evaluate the safety mechanisms on the machine and determine whether there are any biological signs of cellular damage caused by the scans.

In addition, the bill would require the TSA to place prominent signs at the start of checkpoint lines informing travelers that they can request a physical pat-down instead of going through the scanner. Right now, the TSA has signs in front of the machines noting that passengers can opt out. But the signs mostly highlight the images created rather than possible health risks.

The bill is the latest volley in a back-and-forth between Collins and the TSA. At a hearing in November, TSA administrator John Pistole agreedto a request from Sen. Collins to conduct a new independent health study.

But a week later at another hearing, Pistole backed off the commitment citing a yet-to-be-released report on the machines by the Department of Homeland Security’s inspector general.

“I have urged TSA to move toward only radiation-free screening technology,” Collins said in a statement to ProPublica. “In the meantime, an independent study is needed to protect the public and to determine what technology is worthy of taxpayer dollars.”

The TSA uses two types of body scanners to screen passengers for explosives. The X-ray machines, known as backscatters, look like two refrigerator-size blue boxes and are used at Los Angeles, Chicago O’Hare, New York’s John F. Kennedy, and elsewhere. The other machine, which looks like a round glass booth, uses electromagnetic waves that have not been linked to any adverse health effects. Those machines are used at airports in Dallas and Atlanta, among others.

The TSA says the radiation from the X-ray machines is minute, equivalent to that received in two minutes of flying at altitude. That measurement has been verified in previous tests by the Food and Drug Administration, the Johns Hopkins University Applied Physics Laboratory and the Army Public Health Command.

“All the previous independent testing showed that the machines are well below the national standard,” TSA spokesman Greg Soule said.

A group of vocal critics, primarily based at the University of California, San Francisco, has cast doubt on those tests, suggesting that the device used to measure the radiation isn’t equipped to provide accurate measurements on body scanners, among other flaws.

While not commenting specifically on the drafted legislation, Soule said, “the TSA is committed to working with Congress to explore options for an additional study to further prove these machines are safe for all passengers.”

A Transportation Security Administration volunteer demonstrates a full-body scanner at O'Hare International Airport on March 15, 2010 in Chicago. (Scott Olson/Getty Images)

(Michael Grabell, ProPublica) This is part of our year-end series, looking at where things stand in each of our major investigations.

It has become routine for airline passengers across the country: Instead of walking through a metal detector, they now step into a body scanner, hold their arms over their heads and wait until a machine peers through their clothing to make sure they're not hiding explosives.

The Transportation Security Administration has deployed more than 500 of the body scanners, which they call "advanced imaging technology." And the agency plans to install them at nearly every security lane by 2014.

The TSA has insisted that the new scanners present "no health or safety concerns for any passenger." The agency has said they have been used around the world. And it has reiterated that the machines were evaluated by the Food and Drug Administration, leading many to believe that one of the government's top safety regulators approved the technology.

But a ProPublica/PBS NewsHour investigation this year detailed how the TSA had glossed over cancer concerns about one kind of scanner that uses X-rays. In independent, peer-reviewed studies, radiation experts concluded that the X-ray scanner could cause six to 100 airline passengers each year to develop cancer. Outside the United States, few countries use X-ray imaging machines, also known as backscatters, in their airports. And the FDA has no authority to approve body scanners before they are sold because they are electronic products, not medical devices.

In 1998, an FDA advisory panel recommended a federal safety standard for the X-ray scanners. But the agency decided to go with a voluntary standard set by an industry group made up mostly of manufacturers and government agencies that wanted to use the machine.

In November, the European Union decided to prohibit X-ray body scanners in European airports. In the United States, members of Congress have pushed the TSA to conduct a new, independent safety review. And in Florida earlier this month, Broward County commissioners voted [6] to demand the TSA prove that the X-ray imagers at Fort Lauderdale-Hollywood International Airport are safe.

The TSA uses two types of body scanners:

• The backscatter X-ray machine looks like two blue boxes and is used at major airports, such as Los Angeles, Chicago O'Hare and John F. Kennedy in New York.
• The millimeter-wave machine looks like a round glass booth and is used at hubs such as Atlanta, Dallas-Fort Worth and San Francisco.

The X-ray scanner emits extremely low levels of ionizing radiation, a form of energy that strips electrons from atoms and damages DNA, potential leading to cancer. That risk, although small, has led some prominent scientists to ask why the TSA doesn't use just the millimeter-wave scanner, which uses low-powered electromagnetic waves that have not been linked to adverse health effects.

The TSA has said that keeping both technologies in play encourages the manufacturers to improve detection capability while lowering the cost for the taxpayer. The agency says the X-ray machine is safe because the radiation is equivalent to the amount passengers receive in two minutes of flying at altitude.

But ProPublica found some potential problems with the millimeter-wave scanner. Several other countries have reported a high rate of false alarms caused by innocuous things, such as folds in clothing, buttons and even sweat.

Other studies and a congressman briefed on classified tests have suggested the scanners could miss carefully concealed plastic explosives like the weapon used by the underwear bomber on Christmas Day 2009.

As Congress continues to debate the safety and quality of the body scanners, government investigators are set to release two important reports in the new year. The inspector general of the Department of Homeland Security is evaluating how well the TSA is monitoring the radiation of the backscatters. Meanwhile, the Government Accountability Office is wrapping up an investigation of the machines' detection capability, the results of which are likely to be classified.

The Port Authority is demolishing architect I.M. Pei’s National Airlines Terminal at JFK airport, a modernist structure built in 1970 whose glass walls inspired another name: the Sundrome.