Check out this clip that appears to have leaked online this weekend, without a traceable source. It's a PSA that Tom filmed a while back, which was supposedly shown during CinemaCon earlier this year and ahead of a 'Top Gun' screening there in Vegas.

Watch ... you see Tom standing on a biplane that's airborne, literally holding to nothing but a rig and talking into the camera -- which is filming him from another plane across the way.

He says he's filming the latest entry of the 'M:I' series -- seems to be 'Dead Reckoning Pt. 2,' which is currently filming -- and that he's excited to show it to people in on the big screen.

Midway through his speech, he's interrupted by director Christopher McQuarrie -- who's helming both Pt. 1 and Pt.1 -- to tell him that they're losing daylight and need to keep shooting ... this while he's flying his own biplane that pulls up right next to TC's.

Tom signs off by saying he'll see everyone at the movies -- and then, his and Chris' planes simultaneously then dip/nosedive to the left, with Tom simply hanging on ... still standing.

Chris actually posted a photo of Tom doing something just as nuts earlier this year to commemorate his 60th birthday ... with a separate plane shot, confirming the guy's once again doing his own stunts. TC is famous for onscreen feats, especially in the 'M:I' franchise.