Welcome back!
Loons at a hold waypoint will run after the enemy for some distance, but then they will come back again. Exactly what do you mean, stay at a waypoint? If you mean actually stay in position, like at a sentry box, then you'll need a little scripting. If you just mean not move more than 10 yards away ... I dunno, you could still do with a little scripting but you're right, I can't help feeling that a waypoint should do that. What happens if you have a simple move wp synchroed to a trigger so they don't move on till the trigger condition is true?
Don't start a plane on the ground unless it is on a working airfield: silly things happen. Take it's fuel away if you want it to sit on the ground somewhere.