It happens 2 million times each day. And passengers have the routine down cold: Coats off, shoes off, laptops out and for those who still beep — the wand.
Kip Hawley runs the Transportation Security Administration. What grade would he give the agency more than four years after 9/11?
"I'd say about a B-plus," he says.
What's working? Better communication and coordination with the airlines. And it should get better, with a new registered traveler program called "Clear" giving pre-screened passengers a fast pass through security. It's already in place in Orlando, Fla.
"The only complaint we've had is, 'Why isn't this in other airports yet?'" says Bridgett Goersch, security director of Orlando International Airport.
It will be, starting next year.
The TSA also says it continues to confiscatethousandsof scissors, knives and lighters each day. Screeners still come across toy guns and real firearms — 3,000 of them since 9/11.
But critics charge the TSA is far too focused on scissors and not focused enough on cargo. Six billion pounds of it was carried on passenger jets last year alone. An investigation by the Government Accountability Office found only a small percentage is scanned for explosives. Also cited in the report: "The TSA has not taken needed steps to identify shippers who may pose a security threat."
"It only took one pound in the Pan Am Flight 103 over Lockerbie to bring down that plane," says Rep. Ed Markey, D-Mass. "We can't run the risk of not screening every piece of cargo."
The TSA says screening it all would cost billions.
Meanwhile, some critics say there hasn't been enough progress in the terminal.
"For the most part, the TSA screeners today are using the same technology that's deployed pre-9/11," says Douglas Laird, an aviation security expert.
Metal detectors are unable to detect plastic explosives. There is detection equipment available, but it's not in use.
The TSA says it is shaking things up, changing the screening routine so terrorists aren't sure what to expect at checkpoints.
"We're trying to make it simple for the passenger and highly complex for somebody trying to defeat our system," says Hawley.
It's still a system that requires a terrorist to get lucky only once.