On a typical SR-71 mission, the airplane took off with only a partial fuel load to reduce stress on the brakes and tires during takeoff and also ensure it could successfully take off should one engine fail. As a result, the SR-71s were typically refueled immediately after takeoff. This has led to the misconception that the plane required immediate refueling after takeoff due to leaking fuel tanks. However, leaks were measured in drips per minute, and were not significant compared to the overall capacity. The SR-71 also required in-flight refueling to replenish fuel during long-duration missions. Supersonic flights generally lasted no more than 90 minutes before the pilot had to find a tanker.