The longer the flight, the more difficult it becomes to sit still. To arrive at your destination fit, it is good to exercise regularly during the flight.
Pull your toes toward you and push them back away from you. Repeat this exercise.
Draw circles in the air with your feet. Good to keep your ankles flexible. Rotate the circles left and right.
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Pull your knee up toward your chest and hold for a moment. Then switch legs.
Get up now and then and walk down the aisle, for example when you have to go to the toilet.
Round your back by tilting your tailbone toward the chair. Tilt back slowly.
Keep your shoulders flexible by rotating your shoulders. Turn circles forward and circles back. Also pull your shoulders up and push them down again.
Turn your head slowly to loosen any muscles that may have tightened during your nap. Also move your head to the side, with your right ear towards your right shoulder and your left ear towards your left shoulder.
Walk your hands over your shins until you can grab your ankles. Hold this position for a moment before walking your hands back from your shins to your thighs.