11/15/2006. Remarks by Fernando Hoyos: "This aircraft was built under the USAF s/n 52-137 and was delivered to Spain under MDAP (Mutual Defense Assitance Program) in February 1954, and officially accepted by the Spanish AF on May 18, 1954. The Spanish s/n AD.1-2 is hidden by the wing while the USAF s/n 2137 is still carried at the fin. It served into the 1970s."