WASHINGTON (Reuters) - The long-time head of the trade group Airlines for America who helped U.S. airlines win $54 billion in federal COVID relief funds will retire at the end of the year.

Nick Calio, a former aide to President George W. Bush, has headed the influential airline lobbying group since 2011 that includes American Airlines ( AAL ), Delta Air Lines ( DAL ), United Airlines, FedEx ( FDX ) and Southwest Airlines ( LUV ). He has also pushed for more funding for air traffic controllers and battled with the Biden administration over regulatory efforts.

Congress approved $54 billion in three rounds covering much of U.S. airline payroll costs for 18 months during the pandemic. Calio also defended airlines' actions to stay afloat as passenger traffic plummeted.

Last year, Calio urged the Biden administration to take swift action to address a long-standing air traffic controller shortage and out-of-date facilities and technology.

"Business as usual isn't cutting it," Calio said in a speech in Washington last year. "It is an urgent problem. It's easy to ignore maybe on a day-to-day basis, but we have to come up with a plan to address it."

President Joe Biden and Transportation Secretary Pete Buttigieg have repeatedly sparred with airlines, while Airlines for America and some carriers last year convinced a U.S. appeals court to block USDOT's new rule on upfront disclosure of airline fees pending a full review.

The Federal Aviation Administration is still about 3,000 controllers behind staffing targets and has about 10,600 certified controllers.

In June, the FAA again extended cuts to minimum flight requirements at congested New York City-area airports through October 2025, citing a shortage of air traffic controllers.

Airlines have successfully fought against many proposals in Congress in recent years, including one to require "reasonable" baggage fees, a mandate for airline-caused delay compensation or another that could seriously harm the profitable airline credit card business.