OK Bob,
(and please consult other opinions as well , as other people may focus on different things than me)
In order to find out which is the player aircraft in the FMB , open the mission .
If you are lucky , you may spot the player flight by a little flag sticking out of the top of
a waypoint.
Aircraft waypoints are circular. Other chiefs (vehicles , ships etc) are not.
When you click on a waypoint , the flightpath will flash.
Click the "View" button in the top right of the menu tab at the top of the screen.
If you are not lucky , you will need to click on one waypoint of each flight at a time.
When you click on a waypoint a submenu will appear with the tabs :
Properties , Waypoints , Waypoint Options and one numbered tab for each aircraft in the flight ( a max of 4 is allowed by the game).
Click on the tabs for each aircraft one at a time.
As soon as you open the aircraft tab , there will be a small white square with "Player" beside it. If this box has a checkmark in it , it is the player aircraft.
If you click on an empty white box , you must beware that you are selecting the current aircraft as the player aircraft , and will affect the mission significantly - the player will now fly an aircraft unintended by the designer. If this is in a campaign this will likely produce a whole string of problems , but experienced campaign designers will need to speak to this.
Kopfdorfer