A long flight is one of the few places left with no notifications, no drop-ins, and no meetings. That makes it some of the most valuable focus time you get all month, if you plan for it instead of drifting through another movie.
Decide your flight task before you board, and make it something that benefits from deep focus: a strategy memo, a review of a long document, or planning the quarter. Download everything you need in advance, because onboard connectivity is a coin flip. Offline readiness is the difference between a productive block and a frustrated one.
Protect your energy too. Set a stop point so you are not arriving drained. One solid hour of real work beats four hours of half-attention, and it leaves you sharp for whatever waits at landing.