How is it that when Sly comes out of the freezing, icy water, his hair and clothes are bone dry? I don't know too much about hypothermia, but I would imagine that his fairly thin sweater isn't wind proof. I'm sure by the time the movie ended, he would be suffering from more symptoms of hypothermia other than chattering teeth.
The stunt early on in the film where Eric Qualen and his team do the plane to plane transfer was performed by British stuntman Simon Crane. The stunt was performed at an altitude of 2.95 miles (4.75 km) and was the most expensive stunt ever performed costing £568,000(£1 million). Sly Stallone is said to have reduced his fee by that amount to ensure the stunt was made.