Updated

Airline and pilot organizations have filed suit in a bid to stop the Federal Aviation Administration from going through with furloughs set to kick in this weekend, echoing the claims of congressional Republicans that the agency could have found the savings elsewhere.

The suit comes after FAA Administrator Michael Huerta testified Thursday that the public should expect flight delays as furloughs take effect Sunday for air traffic controllers. He said FAA officials could find no other way to cut $637 million from the agency's budget as required by the sequester.

But two airline trade associations and the Air Line Pilots Association said Friday they have filed a lawsuit asking a federal court in Washington to block the furloughs -- though the court is unlikely to schedule a hearing until next week, after the furloughs have begun.

"The impact of these cuts on our industry cannot be overstated," said Faye Black, vice president of the Regional Airline Association, which joined the suit.

The groups joined congressional Republicans in arguing that the FAA was acting inappropriately. While the FAA announced Thursday it was moving ahead with furloughs, the Transportation Security Administration announced that it had found ways to avoid them.

Sen. Tom Coburn, R-Okla., said Thursday that the FAA "has made zero effort" to avoid the furloughs.

"The FAA's decision is a dangerous political stunt that could jeopardize the safety and security of air travelers," he said in a statement.

The FAA has estimated there could be flight delays of about 90 minutes during peak periods.

Coburn claimed the FAA has failed to make "smart cuts" to avoid this outcome. He suggested the agency could reduce spending on "consultants, supplies and travel" by 15 percent, saving $105 million. He also claimed the agency could save much more than that by trimming a grant program for airport improvements.

Huerta said Thursday the furloughs were necessary.

Likewise, the agency sees no way around closing 149 air traffic control towers at small airports that are currently operated under contract for the FAA, Huerta told the Senate Appropriations Committee's transportation subcommittee. The tower closings have been delayed until June 15.

The furloughs and tower closings were designed "to minimize impacts on the maximum number of travelers," he said. But he acknowledged, "We're forced to choose between very unattractive options."

Another Republican lawmaker accused the White House of deliberately trying to upset the public.

"They want to cause the most pain to the American people out there so they will put pressure on Congress to back away from sequestration (spending cuts)," Rep. Bill Shuster of Pennsylvania told a transportation gathering hosted by the National Journal news magazine. Shuster chairs the House Transportation and Infrastructure Committee.

"I believe he (President Barack Obama) is instructing his agencies to do things that inflict the most pain on the most people. This should be laid right at the president's feet," Shuster said.

The FAA's 47,000 employees -- including nearly 15,000 controllers -- are scheduled for one furlough day every other week through Sept. 30. That will reduce the number of controller hours on duty and pay by 10 percent, Huerta said.

In order to maintain safety with fewer controllers, takeoffs and landings will have to be less frequent, and planes will have to be spaced farther apart when they are in the air, he said. That reduces the efficiency of the air traffic system, creating delays, he said.

The impacts may differ depending upon the airport, Huerta said.

The employee furloughs will save an estimated $200 million, and the tower closings will save $25 million, Huerta said.

The Associated Press contributed to this report.