What class are you flying that you have enough free space around you for hands to make any use of a VR headset on the plane?
(Also, even with the space, I'm not sure I'd be brave enough to try and use one in air - adding turbulence and random vibrations on top of the usual VR issues sounds pretty nauseating even as I type it.)
I said mobility is pointless, not mobile. That's an important distinction.
By mobility, I mean the ability to throw the headset around and walk anywhere without worrying about leaving the range of your tether. That sort of thing is important for AR, but I just don't see it mattering for VR in the long run.
There is definitely a market for VR headsets for content delivered by a phone or builtin hardware. Those devices will realistically be limited to seated or standing-room-only experiences, though.