After Challenger and Columbia - a huge on-the-record public enquiry and engineering effort.

After 9/11 - hey, we're holding on to all the evidence we can, and we'll only agree to set up an enquiry if we're bullied into it. (Although we reserve the right to release excerpts from emergency phone recordings of the Towers whenever there's a politically sensitive moment.)

Where are the photos and amateur video footage of the Pentagon attack?

I'd expect a ground level attack would be much less likely to be filmed than an attack on a tall building, for common sense reasons. But did no one take a photo of an airliner flying an approach run on a public building?