U.S. Air Force/Lockheed C-141B Starlifter transports have been cleared to return to service after the left wing on one airplane collapsed during refueling last Dec. 21, 2001 at Memphis (Tenn.) International Airport. The incident sparked the grounding of all 99 C-141Bs in U.S. Air Force inventory, but the limitation was removed Dec. 23 when an initial inspection by an engineering team from Warner Robbins Air Logistics Center in Georgia determined the failure was limited to that specific airplane. According to Col. Russ Cotney, commander of the Memphis-based Air National Guard's 164th Airlift Wing, the incident involved a "human factors error" during the repair of an integral fuel cell at the unit level. The aircraft had accumulated about 39,000 hr. of flying time and had undergone major depot inspection within the past two years. The Air Force has begun a formal investigation into the incident, which led to the spillage of 3,300 gal. of jet fuel and the slight injury of two airmen. The four-engine jet was being fueled for a flight to Ramstein AB, Germany, when the failure occurred. USAF is phasing out Starlifters from active service and replacing them with Boeing C-17s.