LOS ANGELES – A move by federal officials to allow passengers to board planes carrying pocket knives has sparked a backlash by airline workers and is sowing confusion among travelers.

The union representing air marshals has joined flight attendants, pilots and airline insurance firms in calling on the Transportation Security Administration to reconsider its decision to relax a list of prohibited carry-on items. More than 12,000 people have signed an online petition urging President Obama to keep knives off planes.

Even airline management has entered the fray. Richard Anderson, chief executive of Delta Air Lines, sent a letter to the agency Friday saying he, too, opposes the policy change.

Allowing small knives will “do little to speed the screening of passengers” and result in “additional risk to our cabin staff and customers,” the letter said.

This week, the TSA said it would allow air travelers to board U.S. aircraft with small folding knives, golf clubs, novelty bats, hockey sticks, lacrosse sticks and pool cues.

The agency said the move, which would take effect April 25, was aimed at freeing up security officials to focus on bigger threats while allowing passengers a bit more freedom.

But for many travelers, the latest change adds to the confusion that has reigned at U.S. airports since the 9/11 attacks.

“With these changes, can we now bring hair spray, or is that considered more of a threat than golf clubs?” asked Sue Dessayer Porter, a retired market researcher from Portland, Ore. “I’ve even had mascara taken away. It’s good to relax the rules, but how about some consistency?”

As it is, TSA bins are overflowing with shampoo bottles, toothpaste tubes, toy guns and jugs of booze. At Los Angeles International Airport, screeners fill boxes with about 1,400 pocket knives per month.

The list of banned items, from brass knuckles to drill bits, includes nine categories with more than 70 individual items, and has been expanded and revised several times.

TSA officials say the list is adjusted regularly in response to intelligence about potential terrorist threats. But confusion, the TSA says, cannot be blamed on a lack of information.

The agency distributes pamphlets and news releases and posts signs at airport terminals explaining the list. The federal agency even created a smartphone app that answers the question: “When I fly, can I bring my … ?”

“Some people just don’t know what is prohibited and others just forget and don’t think twice that the ceremonial knife that they used to cut their wedding cake is still a knife,” said TSA spokesman Nico Melendez.

But how do you explain, he said, that 1,800 passengers last year tried to bring guns — loaded and unloaded — into planes?

One factor in the confusion might be that the list of prohibited items has evolved over the years and includes what passengers say are contradictions.

For example, common lighters were removed from the banned list in 2007 but torch lighters are still prohibited. Novelty baseball bats under 24 inches will be allowed after April 25 but night sticks are still banned.

You can bring a book of matches but not the kind that you can strike on any surface.

Knitting needles are allowed and so are screwdrivers under 7 inches long, but not ice picks.

Joni Zuckerbrow-Miller, a health care worker from Los Angeles, doesn’t see the logic of the list, particularly the prohibition of yogurt in containers larger than 3.4 ounces.

“We all want to be safe,” she said. “I feel no safer knowing yogurt is banned.”