The symbol with the game currency above the hangar means that one of your planes returned with an item from the flight but all the runways were occupied and it moved directly to its hangar. Just press the symbol to get the profit and you will have an opportunity to send the plane to flights again. If you collect coins for a completed flight while a plane is on a runway (you'll have to land the plane yourself to do that) and not in a hangar, you are going to get additional profit!
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