The Air Force's C-17 Globemaster was chosen last week to fly Keiko, the killer whale star of "Free Willy," back home because the rugged cargo plane is uniquely suited to land on the short runway at Iceland's Heimaey airport. It's not as well equipped, unfortunately, for one of its primary missions: dropping parachuting G.I.'s rapidly into the world's hot spots. It seems that in flight, the hulking 300-ton plane kicks up a lot of turbulence. Such swirling atmospheric eddies can entangle soldiers in their parachute lines, collapse their chutes or hurl airborne paratroopers dangerously into one another. The Globemaster suffers particularly in comparison with its predecessor. A fleet of older C-141's can fly over a drop zone and unload a brigade of 3,000 paratroopers in as little as 19 minutes, with each group of three C-141's separated by 8,000 feet. Not only does that allow for a fast drop, it also minimizes the time the planes spend over a potentially hostile area. But the C-17 creates such a wind wake that the Air Force is keeping each trio of planes 40,000 feet apart. That distance -- nearly seven miles -- stretches delivery time to 51 minutes. "It really slows up our ability to get troops on the ground," an Army officer says. Boeing, the plane's builder, is working with the Air Force and Army to figure out how to fly C-17's closer together without jeopardizing paratroopers.