United Airlines faces possible $1.15M fine from FAA over pre-flight system check

United Airlines is facing a possible $1.15 million fine after allegedly conducting flights with planes that hadn't undergone a certain safety check, federal regulators said, though United called the check "redundant" given other systems.

The Federal Aviation Administration (FAA) proposed the fine on Monday and said that from June 2018 to April 2021, United removed the fire system warning check from its Boeing 777 pre-flight checklist -- an inspection task required in its maintenance specifications manual.

United operated more than 100,000 flights with the Boeing 777 during this time, according to a letter from the FAA.

"Removal of the check resulted in United's failure to perform the required check and the operation of aircraft that did not meet airworthiness requirements," the agency said in a news release.

United, however, said it changed its pre-flight checklist in 2018 "to account for redundant built-in checks performed automatically by the 777" and that the FAA reviewed and approved the change at the time.

"The safety of our flights was never in question," United said in a statement.

The airline said it will review the proposed penalty and "respond accordingly."

"The fire test on a jetliner, like the 777, is really very comprehensive," ABC News contributor and former commercial pilot John Nance explained in an interview. "It's just testing for all the circuitry to make sure that everything is working right."

"The airplane actually does this itself, but it has been traditional for pilots to follow up and do a test," Nance said.