From a window seat in coach, it often seems like turbulence strikes for no reason. You’re flying through cloudless skies when suddenly the plane shakes and the seat-belt light dings on. It would be nice to think that the pilots, at least, saw the rough air coming, but often they’re caught by surprise, too.

That may be about to change. A recent study by the National Center for Atmospheric Research, or NCAR, proposes a new explanation for why turbulence crops up. It owes to something called atmospheric “gravity waves.”