I think the terrorists would keep their passports with them because, well, where else would they leave them? In a hotel room, for the authorities to find afterwards, making the investigation easier? Or on their person, where more than likely they will be burnt/lost/destroyed? Makes sense to me.
Also, in point of fact, "freefall" is not a speed. When you are in freefall, you are under acceleration. Sorry to be so picky.
On second thought....when you reach terminal velocity, are you still in freefall? I'll have to think about that one....
I think we are reading too much into things about the passport.
The hijackers are Foreign Nationals and are REQUIRED to carry their passports with them while in the USA. Same as you and me, (if you are yankee american) by strict reading of the rules, you are required to carry you passport while in Jolly old England, Italy, or China.
Not that anyone has asked to see your papers on the streets of Manchester, or Milan, or Xian, but in theory, you are supposed to be carrying your passport.
Same thing here in the USA - the hijackers (by the rules) are supposed to be carrying their passports at all time. They wouldn't want their whole plot to be thwarted, because one of these swine forgot a simple thing like a passport.
Now, on the freefall thing - we are talking about freefall and Terminal velocity in real world, not lab conditions. The quote is from Sport Parachuting by Russ Gunby, pg 63:
"Sooner or later the speed and friction will balance each other and when the balance of these two forces is reached, the falling object will then have reached a steady falling speed which is called terminal velocity. In atmosphere this takes about 12 seconds and is approximately 176 feet mer second or 120 miles per house. Once terminal velocity is reached, an object will not fall any faster."
Lets not read things that aren't there, or get bogged down by the CTer's in ability to understand science, or use the terms properly.
