The Transportation Security Administration will begin allowing pocketknives and other potential weapons onto commercial airlines beginning April 25.

It would be nice to believe the world has become a safer place in the decade since terrorists killed almost 3,000 people in coordinated attacks involving four commercial airliners.

It also would be entirely naive.

The al-Qaida terrorist network that pulled off the attacks of Sept. 11, 2001, may be weakened by the targeted killings of its leaders, but it still exists. So do an unknown number of both domestic and foreign threats. Extremists would like nothing more than to inflict another major wound on Americans.

So, it is curious that the Transportation Security Administration has decided to let passengers carry folding knives with blades up to 2.36 inches long and less than one-half-inch wide onto planes, beginning April 25. TSA also determined that novelty-size baseball bats, toy plastic bats, billiard cues, ski poles, hockey sticks, lacrosse sticks and two golf clubs are OK inside carry-on luggage.

Any one of those items could be fashioned into a deadly weapon by someone set on crashing an airplane.

The latest measure by TSA is part of a gradual easing of security measures since the initial reaction to 9-11. The new policy aligns U.S. security standards with international rules. TSA says the change will allow it to focus on more serious safety threats.

The agency also cites improved security from the presence of armed pilots, federal air marshals and airline crew members trained in self-defense. Not all flights, however, have federal marshals or pilots armed with guns.

The growing list of opponents to the new rules includes the head of Delta Air Lines, Flight Attendants Union Coalition, the president of the Federal Law Enforcement Officers Association and the Coalition of Airline Pilot Associations.

According to The Associated Press, Delta CEO Richard Anderson said in a letter to the TSA that allowing knives on planes will “add little value to the customer security process flow in relation to the additional risk for our cabin staff and customers.”

We understand that law-abiding passengers are tired of being hassled, harassed and humiliated just to board a commercial flight. We understand TSA’s wish to speed up the boarding process and focus on what it perceives as more serious threats. We understand the concept of acceptable risk in relation to costs and practicality.

But commercial airlines continue to be a potential and attractive target for terrorists because of their vulnerability once they leave the ground.

This is no time to let down our guard. TSA, perhaps with pressure from Congress and President Barack Obama, should reverse its decision.