Do you want to create it as a standalone software using Unreal engine? Because the whole world is already modelled (to a degree) in Microsoft Flight Simulator, with numerous airports created by hand by crowds of third party developers, and let me tell you, it took the whole flight sim community worldwide just over 40 years to get to this state.
So your project definitely doesn't lack ambition.
On the other hand, if you were to use what already exists in MSFS and just add airport interior models with the services you want to simulate, that could create an awesome experience.
Unfortunately I'm unable to help much with either unreal or MSFS integration
Good luck.