I'm assuming from your past posts you have installed PAI a/c and flightplans.

Are you talking about fictional commercial a/c, or all fictional a/c?...just the a/c or their flight plans too?

Did you try the PAI default flight plan removers, as suggested in response to one of your eariler post?
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To manually 'remove' the fictional aircraft, the easiest way is to replace them with some of your real world AI aircraft. How to replace aircraft is discussed in the 'aircraft.txt' section on the TTools help file. Your real world a/c would then fly the flightplans in place of the default fictional a/c.
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If what you want to do is remove default a/c flightplans, the PAI remover does just that. There are seperate removers for commercial and ga a/c.

To do that manually, requires that you delete the line from the 'flightplans.txt' for each flight plan you wish removed. A daunting task if you wish to remove selected flightplans.  



Dave