Damn AI flight plans !!

Now :I've tried several times to build my own flight plans with ttool by modifying the flight plan file. The point is that some of the aircrafts supposed to depart don't even appear. I've tried changing departing time (supposing it was wrong) but did not work either. Some planes instead appear and fly, confirming that the procedure to build a flight plan is correct (last ICAO code in the line is departing airport - the first 00:00:00 which appears in the line is the departing GMT time). Now I wonder what the hell is wrong. Traffic percentage is correct (set at a minimum of 10%). Any of you has an idea of what could be wrong or what to check or to try ?
Any help or idea is appreciated from all of you guys...
Thx

Thx