Sent some bug reports about stuck service cars, an UI-bug, some pax running around in the nowhere and, finally, flightplanner problems, as I can not reschedule flights any more…
And, unfortunately, remote stands are still having problems with processing in time. still boarding starts to late and causes delays… 
Nevertheless Version 29.3-3 and/or 29.4-0 are a huge improvement in performance. and it seems as if pathfinding made a huge step forward - even if I hadn’t tested it with a bigger airport, yet.
Thanks to you, @Fredrik and @Olof !
PLEASE keep on optimizing and bugsolving existing features, before implementing new stuff!