Lawmakers grilled TSA administrator John Pistole about his decision to allow small pocket knives, golf clubs and even hockey sticks on planes.
"This is a big deal," said Rep. Bennie Thompson of Mississippi, "and I'm trying to figure out how this could not be perceived as something potentially dangerous to people on planes."
Pistole said hardened cockpit doors have made it extremely difficult to hijack a plane with a knife, and he'd rather have airport screeners focus on bigger threats, such as improvised explosive devices.
"A small pocket knife is simply not going to result in the catastrophic failure of an aircraft," Pistole said.
The decision has set off a firestorm, with major airlines and unions representing airplane crew members voicing outrage.
On Thursday, flight attendants and TSA screeners gathered at the Capitol.
"No matter how you slice it, a knife like this is a weapon, and it doesn't belong on an airplane," said Laura Glading, president of the Association of Professional Flight Attendants.
Box cutters like the ones the 9/11 hijackers used would still be banned, but the new policy allows folding blades less than a half inch wide.
A bill has been introduced in Congress to stop the agency's plan from getting off the ground.