So this didn’t work in my case.
I don’t want to hijack this topic, but since @gonudo his problem is solved and I don’t want to clutter… 
But this didn’t start since last update, this also happend on Beta 2 (before that my last play was Alpha 20 somewhere i guess)
The airport only has 500 passengers
Specs:
I7-8750H 2.2 ghz (in game running at pretty high frequency and temperature on 4 of the 6 cores up to 91 degrees C) Normally this happens on games like GTAV and Tomb Raider on full specs
DDR4 16 GB
NVidea GTX 1060 DDR5 6GB
But this didn’t start since last update, this also happend on Beta 2 (before that my last play was Alpha 20+ i guess)
It might be the savefile, started a quick sandbox with 500 passengers and all is smooth. Maybe it has to do with my previous bug report on the 3 contractor buses queuing in this topic [SOLVED] Contractors do not work - #5 by Patje89