The Bureau of Transportation Statistics (BTS) gives wheels-off times for both United flights from 9/11, different from those in the 9/11 Commission's Report. Furthermore, the BTS doesn't display wheels-off times for the American flights. They could also be inconsistent.
The BTS (www.bts.gov) displays the actual departure times (push-back times) and wheels-off times as follows:
American 11 0:00 0:00 (ie. not reported)
American 77 0:00 0:00
United 175 7:58 8:23
United 93 8:01 8:28
The numbers used by the 9/11 Commission (United):
United 175 7:58 8:14
United 93 8:00 8:42
The discrepancy between the wheels-off times has never been officially resolved or explained.
Please resolve or explain the discrepancy, formally and officially.