Populating staged missions seems to be bugged. How to reproduce:
1) Enter arena. Select staged missions, populate. Select myself. Double-click on a plane to assign.
2) Leave arena.
3) Enter Arena. All flights shown empty again (assuming no-one else is in the arena).
4) Double-click a plane to assign. Assigning by double click works, except to the plane assigned to in step 1 (double-click unassigns when trying to)
5) While assigned to a plane, leave arena. Enter arena again.
6) Try to assign again. Now the double-click to assign unassigns for the planes assigned to in steps 1 and 4
...
It seems to not forget an assignment when leaving.
