Man Appears to Pee in Middle of Plane Aisle in New Pictures

Say goodbye to the "Yellow Submarine" and enter the 21st century with the "Golden Aeroplane" ... 'cause new photos appear to show a man whipping it out and taking a piss in the middle of an airplane cabin.

Pictures of the passenger allegedly peeing are circulating online ... capturing a dude in a red baseball cap standing up on an American Airlines flight from Chicago to New Hampshire -- though the flight reportedly never made it, diverting to Buffalo.

Seems clear why the flight couldn't make it all the way to New Hampshire ... and, another photo captures the plane's reception on the tarmac -- where it looks like a cop hops onboard, ready to take away the seemingly uncouth urinator.

According to reports, a man named Neil McCarthy was arrested and charged with indecent exposure. Fox Business, citing the criminal complaint, says he told cops he drank several Jack & Cokes before hopping on a plane in Oregon and several more during his layover in Chicago.

Viral airplane freak-outs are sorta par for the course these days ... just take the woman on a recent United Airlines flight from Miami to Newark, New Jersey who allegedly bit a flight attendant.

When ya gotta go, ya gotta go ... but, probably best to avoid joining this particular mile-high club.

Sources close to the situation tell us Neil has been banned from American Airlines.

An American Airlines spokesperson tells TMZ ... "American Eagle flight 3921, operated by Envoy Air, with service from Chicago (ORD) to Manchester (MHT) diverted to Buffalo (BUF) due to a disruptive customer. The aircraft was met by law enforcement upon arrival at BUF and re-departed shortly after. We thank our team members for their professionalism and our customers for their understanding."