When Joe Flacco touched down at BWI airport near Baltimore this weekend ... there was no fancy limo waiting for him ... no chauffeur ... just a regular bus to the regular person parking lot ... and the $121 MILLION quarterback hopped on it like everybody else.

TMZ cameras rolled when the Baltimore Ravens superstar QB arrived ... and the guy couldn't have been more down to Earth.

First we talked to the 28-year-old about that McDonald's run he went on the day he signed his deal ... and then we watched him hop on the bus to the $12-per-day airport parking lot.

Guy couldn't have been nicer -- signing autographs and taking pics with everyone who recognized the Super Bowl MVP.

For the record, Joe's a french fry guy ... not really into the nuggets.

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