Falling in love means you’re willing to put somepony else’s needs before your own. Flying is freedom with no restrictions. Falling in love requires finding common ground. Flying involves going anywhere you want, whenever you want. Falling in love sometimes means you have to stay in one place, for the sake of the pony who stole your heart. Flying is never-ending, for as long as you want.

Rainbow Dash and Fluttershy have already figured all of this out.