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.