Ignoring the fact that I made mistakes, the last time I wrote scripts in forums...
@(helo distance airbase < 50 && vehicle player == player)
pilot1 assignasdriver helo
pilot2 assignasgunner helo
[pilot1,pilot2] orderGetIn true
~10
officer1 assignascargo helo
officer2 assignascargo helo
[officer1,officer2] orderGetIn true
exit
helo is the name of the chopper
airbase has to be the name of a unit, gamelogic ect close to the helipad
pilot1, pilot2, officer1, officer2 are the names of the ai's
execute the script at mission start
You can also do this with waypoints, syncronisation and so on, like Ding says. A script is just all this written down in a file.