about 8 seconds the light disappearing for up to 7 seconds upon the missile striking the aircraft and igniting the CWT, another light, moving considerably more slowly and more laterally than the first, for about 30 seconds this light descending while simultaneously developing into a fireball falling toward the ocean None of the witness documents described such a scenario. Because of their unique vantage points or the level of precision and detail provided in their accounts, five witness accounts generated special interest: the pilot of Eastwind Airlines Flight 507, the crew members in the HH-60 helicopter, a streak-of-light witness aboard US Airways Flight 217, a land witness on the Beach Lane Bridge in Westhampton Beach, New York, and a witness on a boat near Great Gun Beach. Advocates of a missile-attack scenario asserted that some of these witnesses observed a missile; analysis demonstrated that the observations were not consistent with a missile attack on TWA 800, but instead were consistent with these witnesses having observed part of the in-flight fire and breakup sequence after the CWT explosion. The NTSB concluded, "the witness observations of a streak of light were not related to a missile and that the streak of light reported by most of these witnesses was burning fuel from the accident airplane in crippled flight during some portion of the postexplosion, preimpact breakup sequence". The NTSB further concluded, "the witnesses' observations of one or more fireballs were of the airplane's burning wreckage falling toward the ocean". Possible ignition sources of the center wing fuel tank To determine what ignited the flammable fuel-air vapor in the CWT and caused the explosion, the NTSB evaluated numerous potential ignition sources. All but one were considered very unlikely to have been the source of ignition. Missile fragment or small explosive charge Although the NTSB had already reached the conclusion that a missile strike did not cause the structural failure of the airplane, the possibility that a missile could have exploded close enough to TWA 800 for a missile fragment to have entered the CWT and ignited the fuel/air vapor, yet far enough away not to have left any damage characteristic of a missile strike, was considered. Computer simulations using missile performance data simulated a missile detonating in a location such that a fragment from the warhead could penetrate the CWT. Based on these simulations, the NTSB concluded that it was "very unlikely" that