Faisal Shahzad

Minutes after the alleged Times Square bomber was added to the no-fly list last week, several airlines received calls from U.S. officials telling them to check the no-fly list immediately, but the airline that sold Faisal Shahzad a one-way ticket to Pakistan did not receive such a call, according to an administration official and an FBI official.

The FBI had asked the Department of Homeland Security to contact the nation’s top five air carriers and tell them to check the no-fly list right away, according an FBI official.

“The whole idea was as a redundancy,” said the FBI official. “In addition to adding him to the no-fly list, it was to contact the five major carriers.”

Shahzad was added to the no-fly list at about 12:30 p.m. on May 3, and three minutes later the Transportation Security Administration and Department of Homeland Security issued an electronic alert to all airlines notifying them that someone had been added to the no-fly list, according to the administration official.

By law, the airlines had 24 hours to check the no-fly list for the new name. The FBI, however, requested that Homeland Security officials call the top five airline carriers immediately, according to the administration official and FBI official.

But, the administration official said, Homeland Security officials were asked not to call any other airlines, with investigators worried that calling too many airlines could encourage leaks to the media or the disclosure of other sensitive information.

The FBI official took issue with that account.

“There was never a conscious decision to exclude anyone,” the FBI official said. “It was above and beyond the process to add a layer of redundancy.”

Either way, Emirates Airlines had been notified that someone was added to the no-fly list when Shahzad, a naturalized U.S. citizen, used cash to buy a one-way ticket to his native Pakistan.

A law enforcement official said calling just a handful of airlines may have had benefits to the investigation, which was still unfolding at a fast pace.

Not only could leaks to the media scare Shahzad from going to the airport, but he could have run away if the Emirates Airlines ticket agent at John F. Kennedy International Airport told Shahzad he was placed on a no-fly list, the law enforcement official said.

At a press conference hours after Shahzad’s arrest, FBI Deputy Director John Pistole called Shahzad’s placement on the no-fly list “a key step” in the investigation, saying Customs and Border Protection officers did “an outstanding job” in identifying Shahzad as an Emirates Airlines passenger.

In addition to any watchlists or no-fly list, the U.S. Customs and Border Protection agency provides what many officials have called another “layer” of security.

“The no-fly list, in many cases, prevents you from purchasing a ticket,” White House spokesman Robert Gibbs said at a press briefing after Shahzad’s arrest. “But there is another check, through Customs and Border Protection, in order to ensure that we’re checking the manifest, both coming and going, of flights.”

Since the Times Square bomb attempt, the U.S. government has begun requiring airlines to check the no-fly list within two hours of notification that a name has been added. Gibbs called it a “common sense” approach.

An FBI spokesman in Washington did not immediately respond to a request for comment. A spokesman for the FBI’s field office in New York City, Supervisory Special Agent Rich Kolko, also declined comment, saying, “We don’t discuss specific operations or investigative techniques.”

Delta Airlines, one of the leading carriers in the United States, did not immediately return a call from Fox News.

Federal prosecutors in New York have charged Shahzad with five counts, including attempted use of a weapon of mass destruction.