Neither ... nor
Nothing should be in the clouds (except water waiting to precipitate).
Neither aeroplanes nor data should reside in clouds for the same reasons. It's hard to see whom else is sharing your space, and any crashes are catastrophic.
Of course, that doesn't stop the marketing-droids from spruiking about "the advantages of clouds", but then again they can't tell the difference between having one's head up one's arse and having one's head in the clouds.
I like to call that similarity the "Fog Bog™"