Martin XB-51Martin XB 51 airplane model. The Martin XB 51 was an unusual ground attack plane, and one of the most highly advanced aircraft at the time of its first flight in 1949. Two jet engines were carried in pods near the nose and a third was buried aft under the tail. The pilot could vary the thin wing's angle of incidence in the air, making takeoffs and landings easier. The variable incidence wing allowed a very long fuselage which carried two bomb bays,