Why didn't pengers fight back on the 9/11 hijackings?

Four terrorists on each plane, number of pengers these planes carrying. Over a 100. I know for damn sure there were alot of physically able bodied males between 18 and 40 who could've all resisted, so why did these Americans sit in their seats calm as Hindu cows for hours waiting just to die? What percentage of these male pengers were wearing belts that could've turned into deadly devices. Belts can seriously f*ck a guy up. Wrap it around your fist or just start swinging it at someon like a whip. If I had a belt on, some Jihad punk would definately be getting a thrashing.