 Single- and double-engine engine flameouts plagued the program between June 1965 and July 1967, when fuel control problems were finally corrected.No aircraft were destroyed but one was out of service for six months after it crash-landed in a field near Albuquerque.By May 1968 stress cracks began appearing in the wing spars and ribs of all the RB-57Fs outboard of the main engines and numerous groundings forced the cancellation of many operational missions.