विवरण
9/11 revisited - WTC tower design engineers originally took into consideration the possibility of a "fully loaded" Boeing 707 (the largest jet airliner at the time and only slightly smaller than a 767) traveling at 600 mph crashing into the buildings and the resulting "horrendous fire" (their words) from the fuel load. However, the story seems to have changed after 9/11 with the 707 now being a "landing aircraft" flying at low speed with less remaining fuel. Why the change after 9/11?
Aircraft fuel load depends on several factors but It is possible that the hypothetical "fully loaded" Boeing 707 envisioned by the Twin Tower designers, which had only slightly less maximum fuel capacity than a 767, would have carried "more" fuel at its hypothetical impact than the 767's that were claimed to have struck the towers. This is because the 767s claimed to have struck the towers had already burned off much of their fuel load prior to returning to crash into the WTC towers.
The hypothetical impact speed of 600 miles per hour (impossible to attain at sea level) would seem to indicate the WTC designers were envisioning a "worst case" scenario, so planning for the hypothetical 707 to have maximum fuel at impact would seem to fit a "worst case" scenario.
According to the National Institute of Standards and Technology NIST NCSTAR 1-2 WTC Investigation, Chapter 1, Section 1-3: AIRCRAFT IMPACT DAMAGE ANALYSIS :
"Buildings are not specifically designed to withstand the impact of fuel-laden commercial aircraft, and building codes in the United States do not require building designs to consider aircraft impact. However, after the crash of a B-25 bomber into the Empire State Building in 1945, designers of high-rise buildings became aware of the potential of aircraft collision with buildings. Documents obtained from The Port Authority of New York and New Jersey (PANYNJ) indicated that the safety of the WTC towers and their occupants in an aircraft collision was a consideration in the original design. A three-page white paper “Salient points with regard to the structural design of the World Trade Center towers”, February 1964, from the PANYNJ (see Appendix A) indicated that the impact of a Boeing 707 or DC 8 aircraft flying at a speed of 600 mph was analyzed during the design stage of the WTC towers. The paper also addressed the life safety considerations following such impact. The paper stated that “...The Buildings have been investigated and found to be safe in an assumed collision with a large jet airliner (Boeing 707 - DC 8) traveling at 600 miles per hour. Analysis indicates that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact.”
February 27, 1993 article from the Seattle Times titled "Twin Towers Engineered To Withstand Jet Collision" [ http://community.seattletimes.nwsource.com/archive/?date=19930227&slug=1687698 ]:
"We looked at every possible thing we could think of that could happen to the buildings, even to the extent of an airplane hitting the side," said John Skilling, head structural engineer. "However, back in those days people didn't think about terrorists very much."... "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...The building structure would still be there."... Although Skilling is not an explosives expert, he says there are people who do know enough about building demolition to bring a structure like the Trade Center down. "I would imagine that if you took the top expert in that type of work and gave him the assignment of bringing these buildings down with explosives, I would bet that he could do it."
Boeing 707 - 767 comparison :
http://www.whatreallyhappened.com/WRHARTICLES/boeing_707_767.html
September 11 - The New Pearl Harbor (Full version) - Part 1 of 3 https://www.youtube.com/watch?v=I5ppQDmId9M
September 11 - The New Pearl Harbor (Full version) - Part 2 of 3 https://www.youtube.com/watch?v=ahPo6DiGp7Y
September 11 - The New Pearl Harbor (Full version) - Part 3 of 3 https://www.youtube.com/watch?v=haVF4oUOFJE