Washington ? Airline passengers soon will be allowed to carry small scissors and some sharp tools onto planes, but there will be a trade-off: the prospect of more thorough pat-downs and other extra security checks before they get to the gate.

The changes announced Friday by Transportation Security Administration chief Kip Hawley are aimed at catching terrorists carrying explosives, which the agency considers a greater threat than dangerous objects smuggled into an airplane cabin.

Flight attendants and relatives of some Sept. 11 attack victims strongly oppose the change, saying it will make airliners more vulnerable to terrorist attacks.

“They’re just inviting trouble,” said Marcus Flagg, a cargo pilot whose parents died in the plane that crashed into the Pentagon on Sept. 11, 2001.

Airlines and airports generally support the plan, as does the largest pilots’ union.

Hawley said screeners – recently renamed “transportation security officers” – spend too much time looking for objects that don’t pose much of a risk, slowing security lines.

Since the TSA took over airport screening on Nov. 19, 2002, the agency has confiscated more than 30 million prohibited items from carry-on bags. Hawley said about one-fourth of those were small scissors and tools, which will be taken off the list Dec. 22.

Members of the media look over scissors, knives, cigarette lighters and other items that have been confiscated from passengers during a press conference at Reagan National Airport in Washington. Starting Dec. 22, passengers on U.S. flights soon will be allowed to take small scissors and screwdrivers aboard planes again, Transportation Security Administration chief Kip Hawley announced Friday.

As part of the effort to focus on bombs, Hawley said more than 18,000 screeners have received enhanced explosives detection training. As a result, a screener searching a carry-on bag at St. Louis airport found a bomb detonator in November. The person carrying the device was someone who worked with such items and was not a terrorist, Hawley said.

Other changes are aimed at making security checks less predictable for terrorists.

All passengers still will walk through metal detectors, and their carry-on bags still will go through an X-ray machine. But more will be chosen randomly at checkpoints for secondary screening, though the type of extra check may vary; they might be patted down, their shoes may be checked for bombs, their bags may be searched or they may just be checked with a wand.

“By incorporating unpredictability into our procedures and eliminating low-threat items, we can better focus our efforts on stopping individuals who wish to do us harm,” Hawley said.

Pat-downs will be more thorough. Now, screeners only check passengers’ backs and abdomens. Starting Dec. 22 they’ll be checking arms and legs.

Passengers also may notice more bomb-sniffing dogs roaming airports. Hawley said there are now 420 teams of such dogs, 70 percent more than in 2003, at about 80 airports. The TSA also plans to increase the number of walk-through bomb-detection machines from 43 now to 340 by September, he said.

Airline passengers had mixed reactions to the announcement that scissors and tools would be allowed on planes.

“It doesn’t make me feel less safe,” said Mario Ortiz, 32, who had just arrived at Washington Reagan National Airport from Miami for a vacation. “No, because if anybody gets up I’m coming after them.”

Passengers’ willingness to confront terrorists – along with other post-Sept. 11 security changes such as air marshals, armed pilots and bulletproof cockpit doors – are why the TSA believes bombs are now a bigger threat than objects.

But flight attendants say more needs to be done to make commercial aviation safe. The flight attendants’ unions have been lobbying for mandatory self-defense training and for screening of the cargo that’s loaded onto passenger airplanes.

“We are appalled that we are not being listened to by the federal government as they downgrade cabin security standards,” said Tommie Hutto-Blake, president of American Airlines’ flight attendants’ union.

Software consultant Sumil Gubidi, 35, who commutes every week between Dallas and Washington, said the changes give him some pause, partly because of the flight attendants’ opposition.

“If they feel uncomfortable, unsafe, then it’s probably true for everybody,” Gubidi said.

Some members of Congress agree.

“We understand we have to plug new loopholes, but that doesn’t mean we have to unplug the old ones,” said Sen. Chuck Schumer, D-N.Y. Rep. Ed Markey, D-Mass., said he would file a bill to preserve the ban on blades in airplane cabins.

“The Bush administration proposal is just asking the next Mohamed Atta to move from box cutters to scissors as the weapon that’s used in the passenger cabin of planes,” Markey said, referring to the leader of the Sept. 11 hijackers.