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By Harriet Baskas

Transportation Security Administration Chief John Pistole on Thursday stood by his agency's decision to allow some knives and other items on airplanes for the first time since they were banned following the 9/11 terror attacks.

TSA is facing mounting pressure from airline executives, unions representing flight crews, and now lawmakers on Capitol Hill.

"I think the decision is solid and it stands and we plan to move forward," Pistole testified before the House Homeland Security Committee, The Associated Press reported. It's unlikely in these days of hardened cockpit doors and other preventative measures that the small folding knives could be used by terrorists to take over a plane, Pistole said.

"Part of what we do is base our decisions on the intelligence that's out there," Pistole said earlier in the day during an interview on TODAY.

"The challenge becomes if we focus on something that will not cause a catastrophic failure to an aircraft, and miss something that could, then we haven't done our job," he said.

On March 5, TSA announced that some knives under two and a half inches and some previously banned sports equipment, including hockey sticks, will be allowed back on airplanes.

TSA says the change to the prohibited items list is “part of an overall risk-based security approach” allowing employees to better focus on “finding higher threat items such as explosives.”

But groups representing airline industry workers, including many flight attendants, pilots, TSA officers and federal air marshals, have come out against what they characterizes as a dangerous and “ill-advised” move.

This will “put law enforcement officers and the flying public at greater risk," said Jon Adler, president of the Federal Law Enforcement Officers Association.

Several members of the House committee share those concerns and urged Pistole to reconsider his position, AP reported.

'We object'
The Teamsters, as well as the United Steelworkers and some passengers rights groups have also stated their opposition to the new TSA rules and executives at American Airlines, US Airways and Delta Air Lines have written letters directly to the TSA chief.

“We object to the agency decision to allow small knives back in the airplane cabin,” Richard Anderson, Delta’s chief executive officer, wrote in a letter dated March 8th. In a letter dated March 12, American Airlines senior vice president William Ris encouraged TSA “to reassess its proposed revisions to the prohibited items list.”

Southwest Airlines “is engaged with TSA in discussions,” spokesman Chris Mainz told NBC News. United has also expressed concerns to the TSA about the policy, but on Thursday a spokesperson declined to offer specifics.

The airline trade group Airlines for America was originally in support of TSA’s approach to “combining its vast experience with billions of passenger screenings with thorough risk-based assessments,” but it has softened its stance.

“We believe additional discussion is warranted before items that have been banned for more than 11 years are allowed back on aircraft,” A4A spokeswoman Katie Connell told NBC News.

A petition asking the White House to stop the TSA changes now has over 30,000 signatures. Earlier this week, Rep. Ed Markey (D-Mass.) introduced legislation with Rep. Michael Grimm (R-N.Y.) aimed at blocking the changes as well.

The Associated Press contributed to this report.

Find more by Harriet Baskas on and follow her on Twitter at @hbaskas