CANNON AIR FORCE BASE, N.M. — Over a New Mexico training range named the Hornet, two Osprey aircraft speed 100 feet off the ground, banking hard over valleys and hills as they close in on a dusty landing zone. A flight engineer in the back braces a .50-caliber machine gun over the edge of the Osprey's open ramp as desert shrubbery blurs past. The aircraft's joints shift and rattle, and there is little steady to hold on to until the Osprey touches down with a bump, flooding seats with rust-