[lainga]

You could wrap the cabin interior with OLED panels that are normally active and opaque during flight.

Then, when you're on a longhaul and it's time to wake the passengers up - turn them off in midair. Good morning!

[jackhack]

Brilliant. If the sudden increase in luminosity didn't wake you, the screams of fellow passengers looking through the invisible floor at the ground/Ocean 30,000 feet below would surely do the trick!