And your credibility - what little you had left - is gone.
WTC 1 & 2 were NOT designed to take the impact of a fully loaded 707 at 600mph.
"The two towers were the first structures outside of the military and nuclear industries designed to resist the impact of a jet airliner, the Boeing 707. It was assumed that the jetliner would be lost in the fog, seeking to land at JFK or at Newark.
To the best of our knowledge, little was known about the effects of a fire from such an aircraft, and no designs were prepared for that circumstance. Indeed, at that time, no fireproofing systems were available to control the effects of such fires."
- Leslie Robertson, Lead Structural Engineer on the WTC
I have 2,000 hours on military 707's. For takeoff, rotation at about 140-142 kts, gear up around 170. For landing (flaps down) approach was a little over 150.
So, no, the 707 was not planned for 600 mph.