NEWARK, Nov 24 (Reuters) - The Federal Aviation

Administration will send investigative letters to airlines that

did not comply with required flight cuts at 40 major airports

prompted by air traffic control safety concerns during the

government shutdown, the agency said on Monday.

"We will be sending out letters of investigation to any of

the airlines who we don't feel lived up to the requirement to

reduce capacity," FAA Administrator Bryan Bedford said at a news

conference at Newark airport. Transportation Secretary Sean

Duffy said airlines must comply with FAA orders. "If those

airlines did not comply ... there should be accountability," he

said at the event.