To increase the chances of being in the same package, you have to choose
For the flight 1 A task asking for support
So that the flight 2 can provide a task support
So, concretely, in your case:
F-14: select Strike
f-15:
The script found me a mission after 3 tries.
if it still does not work, I would have another more radical solution, but that CEF will not approve ... ^^