An aircraft cabin is a notably dry environment. Relative humidity in the cabin can be markedly below everyday levels — the main reason many observe that skin dries out and feels tight on long flights.
Practical approaches for long flights: apply a barrier-supported, slightly richer moisturiser before the flight; avoid heavy makeup in the air; drink enough water; and cleanse gently and refresh care after landing.
Other travel factors matter too: climate change (moving from humid to dry), different water hardness and disrupted sleep can temporarily affect skin balance. Simplifying the routine while travelling — gentle cleansing, barrier-supported moisturising, sun protection — is usually safest.