On 19 October 2001, in the first operation of its kind, ODA 555 and 595 were flown from a former Soviet airbase, now named the Karshi-Khanabad Air Base (nicknamed K2 by the Special Forces), in Uzbekistan more than across the Hindu Kush mountains. They flew in two SOAR (Nightstalkers) MH-47E Chinook helicopters, escorted by two MH-60L Black Hawks. Conditions were marginal due to the altitude and icing conditions brought on by the low temperatures. Because the Chinooks didn't carry a centralized oxygen-delivery system for passengers, the troops had to use single-use bailout bottles at high altitude to survive the flight. This meant the mission was one way. The pilots refueled the helicopters at very low altitude under black out conditions, flying using night-vision goggles, and without radio communications, as they had trained to do multiple times. The Black Hawk escort was forced to turn back when they could not clear a pass along the flight route. The MH-47 crew set a world record for combat rotorcraft missions, refueling three times during 11 hours of flight. After refueling, they flew into a sand storm and heavy fog which created near-zero visibility conditions.