WASHINGTON, March 5 (Reuters) - Transportation Secretary

Pete Buttigieg said Tuesday U.S. regulators will keep Boeing ( BA )

"under a microscope" as the planemaker works to address quality

issues.

The Federal Aviation Administration said Monday the agency's

six-week 737 MAX production audit into Boeing ( BA ) and

supplier Spirit AeroSystems ( SPR ) found multiple instances

where the companies allegedly failed to comply with

manufacturing quality control requirements.

Buttigieg told CNBC that air travel is the safest mode of

U.S. travel but "keeping it that way is going to require Boeing ( BA )

to step up and the FAA to keep Boeing ( BA ) under a microscope."