This is my last out of twelve bug reports today as I can't go further with this annoying bug.
This new UI is beautiful but on the old UI, there was a button "automatically accept GA Flight". This button is no more there and I think that this is what's causing the bug.
After having built a basic airport in the hardest mode (250.000$ cash to begin with). Basic airport : 1 small runway, 3 small stands, taxiways and ATC. It is 18:40, I open my airport and I get 3 GA flights that come parking in the stand. The night pass and the planes are taking off in the morning around 6:30 and 6:45. After that, no more GA flight until the late evening where 3 GA flight come parking in the stand ... This is totally unsustainable and you can't even build a small terminal to go further with the game.
I tried to start a game at different locations to see if the nearest city has an impact --> No change
I tried to open my airport in the morning after 6:00 instead of rushing to open it once everything was built --> No change
Maybe look in your code, it might have something related to the "automatically accept GA flights" from previous versions.
--> So last bug report until this is solved.