The structural engineers working on the World Trade Center considered the possibility that an aircraft could crash into the building. In July 1945, a B-25 bomber that was lost in the fog had crashed into the 79th floor of the Empire State Building. A year later, another airplane nearly crashed into the 40 Wall Street building, and there was another near-miss at the Empire State Building.[8] Leslie Robertson, one of the chief engineers working on the design of the World Trade Center, has since claimed to have personally considered the scenario of the impact of a jet airliner—a Boeing 707—which might be lost in the fog and flying at relatively low speeds, seeking to land at JFK Airport or Newark Airport. However, Robertson has provided no documentation for this assertion.[8][9]
NIST found a three-page white paper that mentioned another aircraft-impact analysis, involving impact of a Boeing 707 at 600 miles per hour (970 km/h), but the original documentation of the study, which was part of the building's 1,200 page structural analysis, was lost when the Port Authority offices were destroyed in the collapse of the WTC 1; the copy was lost in WTC 7.[10] In 1993, John Skilling, lead structural engineer for the WTC, recalled doing the analysis, and remarked, "Our analysis indicated the biggest problem would be the fact that all the fuel (from the airplane) would dump into the building. There would be a horrendous fire. A lot of people would be killed," he said. "The building structure would still be there."[11] In its report, NIST stated that the technical ability to perform a rigorous simulation of aircraft impact and ensuing fires is a recent development, and that the technical capability for such analysis would have been quite limited in the 1960s.[12][note 1]
