Might be late to the party but just found out today you can fly a pelican in campaign. For anyone who wants to try, you call in a drop, but immediately after you hang up the phone, postion yourself with the grapple shot so the trajectory flings you to the cockpit (using the comms tower from ground level works well), once you are close enough to the glass if you are holding x (or whatever enter vehicle is mapped to), you will enter the pelican. (But you can’t fly it yet). It will start taking off with you in it, you should get a checkpoint. Once you do, end game, reboot, and there will be a pelican on the ground for you to fly. Enjoy.
A tip: You have to be quick when grappling to the incoming pelican because it leaves quickly and will most likely splatter you a few times (like it did for me) before you are successful.
There is also a video on YouTube about which is where I found this out. I initially thought it was just a mod/hoax, but tried anyway and was suprised. So just punch in something like ‘flying a pelican in Infinite’ I also did it after the game was 100%, not sure if that’s relevant but thought to add it.