WASHINGTON (AP) — The House is expected to take up a bill Thursday to provide long-term authority for aviation programs, but a possible veto looms if lawmakers persist in proposed funding cuts or include a provision strongly opposed by labor unions.

The bill would authorize funding the Federal Aviation Administration at $15.3 billion for the current budget year ending Sept. 30, and $14.8 billion for each of the next three budget years. The agency's budget for the last two years was $16 billion and $16.9 billion.

If approved, the funding reductions come at time when the agency had anticipated a larger, not smaller, budget. The FAA is ramping up its program to move from an air traffic control system based on World War II radar technology to one based on GPS technology.

The program is expected to cost the government as much as $20 billion over the next decade and industry another $22 billion. Much of the rest of the world is either using satellite-based air navigation and air traffic control or planning to upgrade to GPS technology.

FAA Administrator Randy Babbitt has already warned lawmakers that he won't make cuts in areas critical to safety. That means a new air traffic system could be delayed.

"If funding were appropriated at the levels proposed in the bill, the safe and efficient movement of air traffic in the air and on the ground would be degraded — today and in the future," the White House said Wednesday in a statement.

Rep. John Mica, R-Fla., chairman of the House Transportation and Infrastructure Committee, which drafted the bill, was almost apologetic about the measure's funding levels in comments to an aviation industry luncheon Wednesday.

The bill's funding cuts are "within the bounds of what I have to achieve to have it pass on the floor," Mica said.

Alluding to the determination of House Republican to cut federal spending, Mica said, "I venture to say even a Mother's Day resolution that had appropriations tied to it would be defeated."

The bill also contains a provision that would overturn a new rule that makes it easier for unions to organize airline and railroad workers. The rule, approved last year by the National Mediation Board, allows employees to form a union by a simple majority of those voting. Under the old rule, workers who didn't vote were treated as "no" votes.

Republicans complain that the new rule reverses 75 years of precedent to favor labor unions. Democrats and union officials say the change puts airline and railroad elections under the same democratic rules required for unionizing all other companies.

Reps. Jerry Costello, D-Ill., and Steven LaTourette, R-Ohio, are expected to offer an amendment to delete the labor provision from the bill.

Airline pilots and the families of victims of a 2009 regional airline crash near Buffalo, N.Y., objected to an amendment they said would jeopardize safety.

The amendment by Rep. Bill Shuster, R-Pa., would require the FAA to tailor regulations to different segments of the aviation industry rather than set across-the-board safety standards. It would also increase requirements that the agency refrain from issuing safety regulations unless it can show the cost to industry is justified.

Jeff Urbanchuk, a spokesman for Shuster, said the amendment would only apply to future FAA regulations and wouldn't affect regulations the agency is already working on. But opponents of the provision scoffed at that, saying the amendment is broadly written and could easily be interpreted to apply to regulations currently in the works.

"Our experience in Washington has taught us that you have to look at everything through the lens of the worst case scenario," said Kevin Kuwik, who lost his girlfriend, Lorin Mauer, in the 2009 crash of Continental Connection Flight 3407. Congress passed a far-reaching aviation safety bill last summer in response to the issues raised by that accident.

The FAA is currently working on eight separate sets of regulations to implement the bill's provisions. That includes rules, opposed by industry, that would impose new limits on pilot work schedules to prevent fatigue. The law would also require airline first officers to meet the same minimum experience levels as captains, since both pilots are called upon at times to fly planes.

Chesley "Sully" Sullenberger, the former U.S. Airways captain who successfully ditched into the Hudson River two years ago after flock of geese damaged both his plane's engines, said he was extremely concerned that Shuster's amendment will prevent critical safety regulations from being implemented.

"It literally means some people will die who shouldn't have had to," Sullenberger told The Associated Press.

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Associated Press writer Sam Hananel contributed to this report.