These numbers are too high. Let's calm down people.
The Pentagon was being evacuated early - lower casualties.
The WTC towers didn't fall immediately, and evacuations began quickly. The first to collapse stood for at least 20 minutes, the second for over an hour. Moreover, reports indicate that the buildings were not full at 9 am - WTC workers come in later on many floors.
10K is probably in the ballpark - 50K is way too high.
When the WTC was bombed in 1993, it took about 6 hours to evacuate. The elevators are out and you have to stream tens of thousands down stairwells. My heart hopes you are right, my mind tells me the number of deaths and casualties will be very high.
Your figures are probably misconceived. The towers sit on top of the largest subway station in all of NY.