OK, I got it working.
It is a three or four step process.
1. Set your flight in a parked space, use the current mission start time (no delay).
Be sure to check the UNCONTROLLED check box, which is right next to the HIDDEN ON MAP checkbox, right under the callsign dropdown menus.
2. Go the Triggered Actions menu (next in line after the weapons/payload menu) and select Add. You want to select PERFORM COMMAND, and then select START.
Don't waste any time with the conditions menu, that is the part here that doesn't work -- at least not for me. Be sure to post and let us know if you find otherwise. I tested the time condition and the user flag condition. No go on either.
3. Create one-time trigger to activate the flight. The Action you want is the AI TASK. Then you just select your START action for whatever flight you want to trigger.
Until you trigger it that way, you'll see the aircraft sitting there on the ramp, parked, with no pilot in it. Then when you trigger it, you'll the pilot appear in the cockpit and the taxi lights will come on. Magik!
Thanks to ED for implementing this -- a little update in the GUI manual would have been appreciated, but what the hell, we figured it out.
Ripcord