By Mike Stone WASHINGTON (Reuters) -Before strapping into the cockpit of the U.S. Air Force's B-2 Spirit stealth bomber for missions that can stretch beyond 40 hours, pilots undergo weeks of preparation that focuses not only on flight plans,

Designed for long-range missions, the aircraft features rest bunks, a microwave, mini-fridge, and a toilet, features tailored for ultra-long missions conducted in high-altitude, low-oxygen conditions.