(Reuters) -A U.S. government delay on funding a grant program risks worsening a shortage of aircraft mechanics at a time when the country's aging aviation system is already strained by demand, lawmakers said on Monday.

Twenty-one Democratic House representatives, in a letter seen by Reuters to Federal Aviation Administration Administrator Bryan Bedford, questioned the legality of delaying grants previously authorized by Congress. Thanksgiving,  a holiday that falls on Thursday, is one of the busiest U.S. travel periods. 

The letter, signed by lawmakers including Representatives Marilyn Strickland, Rick Larsen and Andre Carson, follows a September Reuters report that attributed delays to government efforts to remove references to diversity, equity and inclusion from grant applications. 

"These ongoing delays are stalling critical aviation workforce development at a time when the industry can least afford it," said the letter. "Any further delay or denial of these critical grants would disregard the law and constitute a dereliction of duty to ensure safety in our skies."    

The FAA said in a statement it will respond to the lawmakers directly.

GRANTS TRAIN PILOTS, TECHNICIANS, MECHANICS

Through the FAA workforce grant program, Congress has approved tens of millions of dollars to train new pilots, aircraft maintenance technicians and mechanics, as planemakers Boeing and rival Airbus ramp up global production.

The U.S. aviation industry faces an expected 10% shortfall in certified mechanics required to meet the country's needs this year, according to the Aviation Technician Education Council. 

The U.S. aviation system has been contending with aging air traffic infrastructure and thousands of delays and cancelled flights due to a recent 43-day government shutdown that strained an existing shortfall of controllers. 

Recipients counting on grants to attract mostly male aircraft mechanics said in September they would need to reapply after the applications are rewritten.

The Trump administration has eliminated DEI-related programs in the government and fired many people who worked on those initiatives.

DEI programs promote opportunities for women, ethnic minorities, LGBTQ+ people, and other traditionally underrepresented groups. 

Republican Trump and his allies say DEI unfairly discriminates against other Americans, including white people and men, and weakens the importance of merit in job hiring or promotion. 

While some technical programs target female mechanics, women account for less than 3% of U.S. aircraft maintenance workers, the ATEC pipeline report said.