The testing was delayed because of some problems with the JT9D engines. For example, the engines stalled if the throttles were moved too quickly. This meant that 747s could not be delivered for many more months. 20 planes were stuck at the factory while they were waiting on engines. On December 13, 1969 the test plane was being taken to have some changes made to it. The pilot, Ralph C. Cokely landed too early and did not reach the runway. One of the landing gears was ripped off, and two of the engines were damaged. However, Boeing took the 747 to the 28th Paris Air Show in mid-1969. There, the public saw the 747 for the first time.