Squeeze a tennis ball or a pair of socks with your hands until they’re tired.
Keep the balls of your feet planted and raise your legs using your calf muscles. If this is too easy, place your carry-on bag on your knees. Continue until tired.
Plant your heels firmly and raise your toes as high as possible. Hold for five seconds, and relax. Repeat until tired.
Place your hands on your armrests and raise your knees slowly (together is harder than one at a time) toward your chin. Lower them slowly. Repeat until tired.
Cross your legs. Rotate the dangling foot in as wide a circle as possible. Continue until tired.
Stretch your neck by keeping your chin close to your throat and tilting your head forward. Roll your head from one shoulder to the other, but avoid rotating it backward.
Flex your trapezius muscles by doing shoulder hunches. Lower your shoulders, and then raise them up toward your ears into a shrug. Hold for five seconds. Continue until tired.
Arch your torso gently backward and forward like a cat.
Flex your gluteus muscles and hold for as long as possible. Squeezing your rear like this may occasion strange glances, but these muscles are the biggest in the human body and need to be exercised, too.