I was watching a piece on the CBS Evening News last night about Flight 93. Due to that plane being the only one on 9/11 where data and sound recorders were recovered, there is a lot of information about that fateful flight and the passengers who fought back, possibly saving the US Capitol from a direct hit.
Curious about whether the airlines still use these flight numbers, I found out that the numbers of all four planes involved in the terrorist attacks had been officially retired by American and United Airlines in 2001. However, in May of this year there was a system error at United in which the numbers 93 and 175 showed up in the system and were quickly removed.
Here's the CBS report from last night in it's entirety with Scott Pelly introducing it from the new Flight 93 Memorial in Shanksville, PA, opening this weekend.