A slight variation:
If you (like me) dont fancy using radiomsgs,
do something like the following to let the chopper know of your decision:
When capturing the lieutenant, make him join your group
badguy setcaptive true
[badguy] join players_grp
And then, when the chopper comes to pick you up, he decides upon his next waypoint with:
badguy in units players_grp
(or simply
group badguy == players_grp
)
If the badguy is in the players group, go home and call it a day, else go to the other port.
And that would go in the condition field of a trigger, replacing the radio-triggers in macgubas example (but keeping the waypoints, syncs and whatnot)