Avoid just sitting and watching or surfing the in-flight entertainment. Plan your entertainment and aim to take regular movement breaks while watching and in between programmes. Many flights have wifi these days but you should avoid watching more than one screen at a time. If you have to work, then do so then take a break and reward yourself with a movement break and stretching followed by watching a film. The aim is to be very conscious about when you are working, switching off with some entertainment or getting some quality rest.
So many people can't sleep when flying so don't worry about it. You could potentially recoup more energy by resting well rather than trying to sleep. Think more in terms of rest rather than sleeping. Use the in-flight guided meditations to help you rest and balance your energy.
Close your eyes, focus on your breathing while mentally and softly repeating the words IN and OUT. Do this for 10-20 minutes on take-off and landing to calm any jitters but also to help to balance out your energy. With your eyes closed you can also visualise or imagine roots coming out from your feet and sending them down to the centre of the earth. This is very grounding and can help to minimise the destabilising effect of flying.
Related to the above, get up and move. Find some space where you can stand with your feet about hip width apart and breathe deeply. On the exhalation imagine sending roots out through your feet and to the earth's centre.
If you're feeling anxious about whether or not you're sleeping, use the rest priniciple described above and avoid constantly checking how much time you have left until landing. Also avoid measuring how much sleep you've had and definitely avoid using a 'smart' wristband device to monitor your sleep pattern
Travel with small bottles of essential oils such as lavender (to aid rest) or eucalyptus (to help breathing and clear stuffy nose and head)