Boeing could be looking at lengthy process to get back in the good graces of U.S. regulators, as a May 28 deadline set by the Federal Aviation Administration (FAA) for an updated safety plan approaches. 

On February 28, the FAA gave Boeing 90 days to put together a plan to address numerous safety and manufacturing issues regulators identified following the blowout of a door plug aboard a 737 Max 9. Ahead of that deadline, FAA administrator Mike Whitaker told ABC News on May 23 that it "is not the end of the process." 

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"It's the beginning, and it's going to be a long road to get Boeing back to where they need to be making safe airplanes," Whitaker said, adding that the FAA has been working with Boeing to draft the new safety plan. 

According to The New York Times, the FAA flagged dozens of manufacturing issues for Boeing's 737 Max aircraft as part of an audit released in March. That included one instance where mechanics for Boeing supplier Spirit were seen using a hotel key card to check a door seal. On May 7, the FAA said that it was also investigating whether Boeing employees may have falsified inspection records for 787 Dreamliner planes. Then on May 14, the U.S. Department of Justice told a federal judge that Boeing could be subject to criminal prosecution for a pair of deadly 737 Max crashes in 2018 and 2019 respectively.