kiloton nuclear bomb. Alert status consisted of an active inventory of 36 Mirage IVs. At any one time 12 aircraft would be in the air, with a further 12 on the ground kept at four minutes' readiness and the final 12 at 45 minutes' readiness, each equipped with an onboard functional nuclear weapon. These 36 active aircraft would be rotated with 26 reserve aircraft; the latter were kept in an airworthy condition or were otherwise subject to maintenance activities. Within the first decade of the type entering service, in excess of 200,000 hours were flown and 40,000 aerial refuelling operations were performed by the Mirage IV fleet alone; at one point, Mirage IV operations were consuming up to 44 per cent of the French Air Force's total spare parts budget. The primary objectives of the Mirage IVA force were major Soviet cities and bases. With aerial refueling, the plane was able to attack Moscow, Murmansk or various Ukrainian cities when sortieing from French bases. A justification of the Mirage IV given by Armée de l'air Brigadier General Pierre Marie Gallois, an architect of the French nuclear deterrent, was that: "France is not a prize worthy of ten Russian cities". In order to refuel the Mirage IVA fleet, France purchased 14 (12 plus 2 spares) U.S. Boeing C-135F tankers. Mirage IVAs also often operated in pairs, with one aircraft carrying a weapon and the other carrying fuel tanks and a buddy refueling pack, allowing it to refuel its partner en route to the target. Even so, some sources state that some of the mission profiles envisioned were actually one-way, with the crew having no chance of returning after bombing a Soviet city. The inability for the Mirage IV to return after missions had been a point of controversy during the aircraft's early development. Both flight and grounds crews received training principally by Strategic Air Forces Command 328, stationed at Bordeaux. Several Nord Noratlas were specially modified, having received the Mirage IV's radar, control consoles, and additional electrical generators, for the purpose of training navigators; these were later replaced by a pair of customised Dassault Falcon 20 outfitted with much of the Mirage IVP's avionics. Transition and upgrades Initially, the basic attack flight profile was "high-high-high" at a speed of Mach 1.85, engaging targets up to a maximum radius of 3,500 km (2,175 mi). In the late 1960s, when the threat of