By May, all College Eyes had been fitted with QRC-248. Ethan Bravo's mission was changed from that of a backup for Ethan Alpha to being the primary QRC-248 listener. However College Eye was prohibited by the Joint Chiefs of Staff from actively "interrogating" MiG transponders, following a National Security Agency security policy protecting its "intelligence sources" (of which the QRC-248 was one) and thus was restricted to waiting for North Vietnamese GCI to interrogate its aircraft. QRC-248 began regular use in July 1967, but by then North Vietnam's MiG force, which had suffered serious losses in May, had suspended its combat ops.