Can you get 2 of the same aircraft?

Good question. You cannot unfortunately.

But if you do have extra duplicate components of same aircraft (i.e. You have stormwind plus some stormwind parts), the best utilization of the latter is to save them to evolve your current stormwind! Hope this helps!

Evolution material requirements can be consulted when analyzing your plane's stats in the "Air Force Command Center" --> "Air Force" --> click your stormwind --> "Air Force Remodelling" --> "Promote"