from gamefaqs:
Start off by leaning forward on the bike to get a
speed boost. Stay on the outside and then cut in. As soon as you touch the
ramp, the cutscene will put you inside the plane. Now, here's where pretty
much everyone will screw up once. You cannot use a gun in here! You can
try, but eventually a stray bullet will blow the plane. Just use you fists,
melee weapon, flowers, or a dildo. Beat the agents to death, then take out
the guy with the parachute. Grab the 'chute, throw the remote explosive,
and stand on the back of the plane. Jump off, detonate it, and watch the
fireworks as you come down. Make sure not to land in the military base, eh?
i'm not sure about not using guns tho, i think if you don't get too triggerhappy you should be able to shoot em without blowing up the plane, especially if u use a handgun.