"Faker", or simulated target aircraft flew mock penetrations into air defense sectors to exercise GDI stations, Air Defense Direction Centers, and interceptor squadrons. Initially using modified B-25 Mitchell and B-29 Superfortress bombers, the aircraft would fly attack profile missions at unexpected, random times and attempt to evade coverage by flying at low altitudes and randomly flying in different directions to confuse interceptors. The aircraft were modified to carry electronic countermeasures (ECM) gear to attempt to confuse radar operators. In 1957, the propeller-driven aircraft were phased out and replaced by Martin B-57 medium bombers which were being phased out of Tactical Air Command. Initially RB-57As from reconnaissance units were modified to have their former camera bays refitted to carry out the latest ECM systems to confuse the defenders. Wing racks, originally designed for bombs, now carried chaff dispensers and the navigator position was replaced with an Electronic Warfare Officer (EWO). The modified B-57s were designated as EB-57 (E for special electronic installation).