In July 2014 there was an uncontained failure of a fan rotor while the aircraft was preparing for take-off. The parts passed through a fuel tank and caused a fire, grounding the F-35 fleet. During high g-force maneuvering three weeks before the flight, flexing of the engine caused excessive rubbing at the seal between the fan blisk and the fan stator initiating the impending failure. The rub caused a temperature of over 1,000 °C (1,900 °F), well beyond the material limit of 540 °C (1,000 °F). Micro cracks appeared in third-stage fan blades, according to program manager Christopher Bogdan, causing blades to separate from the disk. The failed blades punctured the fuel cell and hot air mixing with jet fuel caused the fire. As a short term fix, each aircraft is flown on a specific flight profile to allow the rotor seal to wear a mating groove in the stator to prevent excessive rubbing.