You need to plant a bomb on the plane with a bike, don't be stealthy. Just go for it. You have to start riding immediately and it's dropping things for you to avoid. If you don't race at TOP speed immediately, you'll never make it onto the plane.

Once you TOUCH the ramp you're in so don't worry about driving in properly. Your bike goes overboard immediately. Barrels are rolling down at you - be careful with a silenced pistol to shoot bad guys without hitting the explosives all around you.

The las guy has a parachute. Plant the bomb near the exit then run and fall off the plane - you get a cut scene of you falling. Fall for a while before opening the parachute so it doesn't take you 3 hours to reach the ground. You are VERY high in the sky.

mission passed
$20,000

Be very careful when you're falling not to go into the restricted zone, lest you be shot down like a game bird.

Catalina calls you on your cell phone, she's upset with you.

Grand Theft Auto San Andreas Walkthrough