The Swedish Air Force underwent a rapid modernization from 1945. It was no longer politically acceptable to equip it with second-rate models. Instead, the Air Staff purchased the best it could find from abroad, e.g. P-51D Mustangs, De Havilland Mosquito NF.19 night fighters and de Havilland Vampires, and supported the development of top performance domestic models. When the Saab 29 Tunnan fighter was introduced around 1950, Sweden suddenly had planes that were equal to the best of the Royal Air Force, the Soviet Union's VVS, and the U.S. Air Force.