A powerful movie, despite the fact that you go into it knowing pretty much exactly how it's going to end and nearly everything else that happens. The actors range from obscure to semi-obscure, although I was able to spot Gregg Henry (the oily Val Resnick in Mel Gibson's Payback). (And, although I didn't notice her, little Denny Dillon, a Saturday Night Live cast member a quarter-century ago, also appears as a passenger.) The lack of recognizability drives home the point that the heroism on 93 wasn't Willis- or Schwarzenegger-style, but just ordinary folks doing what the entire might of the US government could not: saving (probably) the US Capitol building and (almost certainly) hundreds of lives on the ground.
The general lack of slick special effects also helps generate a you're-really-there atmosphere. The confusion on the ground is painful to watch; so is the complacency in the air, as a warning against cockpit intrusions is received, but inadequately appreciated.
One moving scene near the end shows both terrorists and passengers saying prayers. In less-skilled hands, this could have been a cheap and stupid anti-religious trope suggesting that only happenstance had made one side the bad guys. Instead (for me, anyhow) it just hammered home the differences between murderers and victims.