Sources with direct knowledge tell us ... the plan for the upcoming Closing Ceremony involves Tom rappelling down from the top of Stade de France ... landing on the stadium field and carrying the official Olympic flag.

The TV broadcast will then cut to a previously recorded film ... and the first 2 minutes shows Tom's journey on an airplane ... flying with the Olympic flag from France to Los Angeles, where he skydives down to the Hollywood sign.

The Hollywood sign stunt was actually filmed on a Saturday morning back in March, and our sources figured someone would spot Tom in the air, connect the dots and the story would leak ... but his descent went completely unnoticed.

Now, there are photos of Tom on the Hollywood sign from back in March, but no one got him in the air ... only after he was already on the ground, and no one had a clue this was related to the Olympics.

We're told the film will then show Tom passing the flag to other Olympians -- including a cyclist, skateboarder and volleyball player -- as they make their way around the next host city for the Summer Games.

In paparazzi footage from March, you can see Tom passing the flag to the first Olympian.

Our sources say logistics for the stunt portion in France are still being worked out ... the Closing Ceremony is set for Aug. 11 ... this is all very complicated, and Tom might have a stunt double do the actual rappelling to kick this all off.

Tom, we're told, is the driving force behind all of this ... and he's actually the one who approached the International Olympic Committee about doing a series of stunts to bridge the Paris and L.A. Games.

Tom's actually been involved in past Olympic ceremonies ... in 2004, he helped carry the torch through Los Angeles as part of a relay across the globe ahead of the Summer Olympics in Athens, Greece.