Travelers who wonder why airlines need gender and date of birth to book flights starting this weekend should know this: It's so the federal government can check them against terrorist watch lists faster than most people can read this paragraph.

Or that's the idea, at least.

The Transportation Security Administration on Saturday will roll out the second phase of its Secure Flight program, which transfers the responsibility of screening passengers from airlines to the federal government.

The first phase launched in May, when carriers began requesting passengers' names as they appear on the identification cards they intend to show when checking in.

In the past, if a customer was named Jennifer, for example, she would be able to book a flight under Jenny or Jenn. Now, she should match her booking name to her ID exactly. Plus, she must provide her gender and date of birth when buying the ticket.

That information will be run instantly through federal databases, said Jon Allen, Transportation Security Administration spokesman. He said the entire process should take only about four seconds.

Allen said airlines will phase in the new procedure with a goal of having every carrier compliant by early next year. He stressed that the program is not expected to slow down travel. Last-minute purchases from an airport ticket counter should require no additional time outside of that four-second computer scan, Allen said.

And the government built in flexibility for passengers who bought tickets prior to the change and did not match their IDs exactly.

"People need not fear they're going to be delayed at the checkpoint," he said.

But Secure Flight, billed as a "behind-the-scenes" process, took its criticism early on, and not only from those with privacy concerns. The program, which was recommended by the 9/11 Commission, came under fire years ago for its own security after a government team found it vulnerable to hacking. Congress required the program meet 10 conditions before giving it the final go-ahead.

Debra Engel, local security director for the Transportation Security Administration, said she has not heard of any problems from carriers as they prepare to apply the program.

Local aviation attorney Mark Fava, a partner at Nelson Mullins Riley & Scarborough, said Secure Flight could make passenger screening easier. Though customers booking online might need to provide more specific information starting Saturday, he said, the program streamlines all the work within a single entity.

An operations attorney for Delta Air Lines for three years after the Sept. 11, 2001, terrorattacks, Fava remembered how the previous process often left airlines in an uncomfortable position if a customer showed up on a watch list.

"The carrier could only look to the passenger who wants to get on the plane and say, 'I'm sorry, but there's nothing we can do at this point,' " Fava said.

Now, he said, air travelers can take up any issues directly with the Transportation Security Administration.