I’m new to Aviatife so it might just be me missing something but adding aircraft to my collection on the Fleet page doesn’t seem to influence the quick jobs at all.
Anything else I need to do - ideally was hoping to use the modded planes in MSFS?
Quick jobs use “only aircraft from basic light and light category”
As @Whiplash said - you are probably trying to use an aircraft from a different “weight” category than the basic light and light category.