Mike Tyson Laughs On Phone After Airplane Beatdown

Here's more proof Mike Tyson didn't have a care in the world after beating up an alleged heckler on a plane last week -- with the boxing legend laughing his ass off on the phone moments after the incident.

TMZ Sports has obtained video of Iron Mike in the San Francisco International Airport after being escorted off his plane to Florida around 10:49 PM on Wednesday ... and the former champ looks happy as a clam as he chats it up on his cell.

A witness tells us Tyson was surrounded by cops ... and was speaking with one of the officers following the incident.

As we previously reported, Tyson was all smiles with a fan as he exited his JetBlue gate ... an interaction that went down just minutes after he was caught on video throwing punches at Melvin Townsend III.

While Tyson doesn't seem to be sweating the whole incident, he could still face legal action ... as Townsend lawyered up with Matt Morgan from Morgan & Morgan.

A rep for Tyson told us the passenger was clearly intoxicated and the altercation broke out after a water bottle was thrown at him ... but Morgan denies his client ever threw anything.