SAC felt the Moroccan bases were much less critical with the long range capability of the B-52 Stratofortresses that were replacing the B-47s . It also had completed USAF bases in Spain in 1959 . SAC felt the Moroccan bases were much less critical with the long range capability of the B-52 Stratofortresses that were replacing the B-47s and with the completion of the USAF installations in Spain in 1959 .