Not until Halo 4 you can't.
By the way, in Halo 4, you can FORGE a pelican! :D
You can't drive a pelican in Halo 3.
OK first that first answer was someone who NEVER! played HALO (WHICH IS AWSOME BY THE WAY!!!) you can't drive one in halo without modding. BUT maybe in Halo Reach you can >: )
yes.
Only in Halo: Custom Edition for PC.
in halo 3 there is none to drive
Not sure what game your talking about when you say "halo marines", but no, you can not drive a pelican in any of the current or upcoming halo games if I'm correct.
It's called a pelican. No, you cannot.
If by jet you are referring to the Pelican dropship, then no.
Unfortunenatly you cannot drive a pelican in halo 3, but there is an Easter egg in halo reach on new Alexandria that let's you drive in a pelican or phantom. Trust me pelicans suck, they're slow, they can't go up, and they can't shoot.
No there is not a mod
No Not really only on halo 1 you can mod to drive one but its ok.
Falcon, Banshee, Longsword, Pelican, and phantom