According to Politico, an inventory was taken by the Air Force after a multi-day trip with the press out to the West Coast last month -- and several items were missing.

The outlet claims it was enough of a problem that the White House Travel Office was alerted ... prompting the WH Correspondents' Association prez to send an email reprimanding her peers. Among the items that were taken ... pillowcases, glasses, and gold-rimmed dinnerware.

The email is said to have slammed the journos for their sticky fingers ... claiming the antics were a bad look for the entire press corp.

Air Force One is famously known for having all sorts of presidential-themed goodies onboard, including boxes of M&Ms, napkins, and matchbooks. These items are, of course, up for grabs ... but over the years even nicer crap has been getting snatched, and now ... it's an issue.

Yet, per Politico, this snatch-and-grab right of passage on Air Force One may be coming to an end. The email sent to the press pool reportedly wasn't accusatory ... but did offer to facilitate a quiet return of any goods potentially swiped from the flight.

WH officials told Politico the email was meant to send a message ... stop stealing or else!!!