Correction: An earlier version of this story incorrectly stated the number of planes hijacked in the Sept. 11, 2001, terrorist attacks. This version has been corrected.

The Transportation Security Administration disregarded the safety of airline passengers and workers with its decision to relax carry-on restrictions beginning next month, according to labor groups representing airline workers.

TSA Administrator John S. Pistole announced Tuesday that the agency would allow small knives, souvenir baseball bats, golf clubs and other swingable sports equipment onto planes starting April 25.

Criticism of the policy has been swift, with one labor group mounting a petition to reverse the decision.

A TSA official said the rules conform with international standards and allow agency personnel to focus more on “finding higher-threat items such as explosives.”

“If our officers can spend less time looking for small penknives and more time looking for explosive devices, we’re better at doing our job of protecting the safety of the American people,” TSA spokesman David Castelveter said Thursday. “A small knife will not enable a terrorist to bring down an airplane.”

Castelveter said aviation agencies have added new levels of security to prevent the type incidents that occurred on Sept. 11, 2001, when terrorists hijacked four planes using box cutters. Cockpit doors are now heavily fortified, and the TSA now uses behavior-detection­ officers to help identify potential attackers, he said.

But labor groups say the new policy is dangerous.

“It’s absurd, this fixation on the cockpit and the plane being used as a weapon of mass destruction” said Veda Shook, president of the Association of Flight Attendants-CWA. “We’re totally on board with that, but there’s everybody else in the rest of the plane.”

Castelveter said that “TSA’s primary mission is to stop a terrorist from bringing down an airplane,” whereas traveler safety is a “tangential or residual benefit of the things we do.”

“I feel safe knowing there are air marshals to get involved if there is an unruly passenger on board,” Castelveter added.

Federal air marshals are not on every flight, and the union that represents the law enforcement officers opposes the new TSA policy.

“They act like everybody on the back side of that cockpit door is disposable,” said Jon Adler, president of the Federal Law Enforcement Officers Association.

The union contends that marshals will face greater risks in confronting dangerous passengers.

“They can execute a first strike and take control of our weapons,” Adler said.

He added that TSA officials did not consult with labor leaders “or any other stakeholder group” before changing its policy.

The Coalition of Airline Pilots Associations said much the same in a statement Thursday. “CAPA is deeply concerned that industry stakeholders were not consulted prior to implementing these changes,” it said.

Castelveter noted that the TSA consulted officials from its subsidiary agencies, including the Air Marshal Service, before making its decision.

The new policy will allow passengers to carry pocketknives with blades less than 2.36 inches long and less than half an inch wide.

Adler noted that a prisoner killed a federal corrections officer last week. He said the inmate stabbed the officer in the neck multiple times with a small knife made of plastic.

The Association of Flight Attendants has created an online petition with the White House to re­­verse the TSA decision.

As of Thursday, the petition had drawn about 5,300 of the 100,000 signatures required for an official response from the Obama administration.