I have had a few planes on INN, BRI, & PRG that would ‘suddenly’ go red but when I look it’s because they are sitting at their gate and you cannot activate any of the services. They kind of get stuck there.
I will try to post a screen shot when I get another one.
Do you have available trucks to service the planes ?
Yes. I do have the available trucks and a lot of times the airport itself is not at Max.
When I leave and go back to the airport then suddenly there are certain services around the plane but the timer is still in the red.
It seems to be a bug. Happens the most to the S-planes but I also had a M-plane with the same problem.