Ideally, you shouldn't wear any make-up during a flight. This will allow your skin to breathe and for any products you apply to fully absorb. Before take-off, use a make-up removal wipe to clean your skin. Then, start your hydration regime. Every two hours, spritz your face generously with a fine mist of thermal water, then apply a hydrating serum to lock it in. When you feel the need, massage into your face your favourite travel-sized moisturiser ; preferably one with an SPF; which will help to reduce any puffiness. Throughout the journey, sip water regularly ; aim for one glass per hour; and apply a moisturising lip balm.