I'm sure someone must have thought of this already, but I've just discovered it for myself and I thought I'd share.
One of the limitations of the game has always been that you have to plot waypoints in advance - you can't really surprise the player with new objectives. For most purposes this is fine - go to X and bomb Y. But what about scenarios where you don't want the player to know ahead of time exactly where to go or what to do? GCI is a good example - nightfighter pilots would climb to altitude and wait "on call" before getting their assigned waypoints. In Korea, the USMC would send up standing patrols of ground attack aircraft, and dispense them to the front as needed - the pilots wouldn't always know their targets before takeoff.
One way to get around this problem is to use a time-delayed escort flight. For example, say you want to set up a flight of F4U's to patrol south of the MLR, but you don't want to the player to know where the hotspot is going to be. You set up a flight with an endpoint at the place you want the player to orbit. At another airbase (somewhere the player won't see), you set up another plane (gliders work well) with the second waypoint at the same spot as the orbit point, then a ground attack waypoint where the battle is going to be, and so on. Set the glider's takeoff waypoint with a time delay of say, 10 minutes. Then, set the player's orbit waypoint to target the second glider waypoint.
When the player runs the mission, they'll go to their orbit point. Ten minutes into the flight, their waypoints will change to those of the glider's, with attack coordinates and everything. AI planes will follow the new flight path, so this can be a good way of getting planes to "hold" at a certain place for a period of time. It's a little crude, but it could be a good way of simulating GCI, Carrier CAP, or spontaneous calls for air support, without giving everything away in the briefing. This could work especially well for variety in random campaigns, where every "routine" patrol looks the same on the map, but could be a different situation every time.
EDIT: Make sure to get rid of the gliders after they've spawned, or you'll have problems with the AI trying to follow them on the ground. The best way is to spawn another glider on top of them after one minute. Their waypoints will remain. By connecting one set of waypoints with another delayed-spawn glider flight, you can actually create a series of waypoints (as long as the previous glider has been destroyed). This can be used to simulate a series of GCI contacts, for instance. Just make sure to turn off the gliders' radio
CY6.