I've had this problem also. I noticed the parking option was gone when this happened. An easy way to fix this is to change the type to something other then "takeoff from parking" and then setting it back to "takeoff from parking". And then select the desired parking number again.
Like takamba said, shooting gallery mission has a JTAC. You wont hear the voice though, cause its still WIP.(its still loads of fun though, so try it out :pilotfly:)