I recently had the similar issue with same error message: "your flight is delayed please wait."
I solved it by checking the map time (the time at mission starts) and the time when the vehicle spawns.
it's set to be impossible to set vehicle spawns time earlier than the map time (logically make sense cause otherwise meaningless)
and the time difference will be the duration of 'delay", thus I set the vehicle spawns time 1sec beyond the map time and the issue solved (although the error message still exsist but I now can take control of the vechicle I placed)
Map time:
Vehicle spawns time:
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