For the purpose of being more comfortable during your flight, and to possibly mitigate the dangerous adverse effects of in-flight immobility, you might consider doing some of the following exercises.  As always, before engaging in a series of exercises, be sure that the exercise will be physically comfortable and medically safe for you.  You can do the following exercises while in your seat:
 

• Foot Pumps
  Foot motion is in three stages:
  • Start with both heels on the floor and point your feet upward as high as you can;
  • Put both your feet flat on the floor;
  • Then, lift your heels high, keeping balls of feet on the floor;
  • Repeat the 3 stages in a continuous motion and in 30-second intervals.
     
• Knee Lifts
  Lift your leg, with the knee bent, while contracting your thigh muscle.  Alternate legs.  Repeat 20 to 30 times for each leg;
   
• Abdominal Suctions
  Before eating, begin by exhaling all of the air out of your lungs.  Then, pull your stomach as high into your rib case as possible without inhaling.  Hold briefly and relax.  Repeat as many times as possible without inhaling;
   
• Ankle Circles
  Lift your feet off the floor.  Draw a circle with the toes, simultaneously moving one foot clockwise and the other foot counterclockwise.  Reverse circles.  Rotate in each direction for 15 seconds.  Repeat if desired;
   
• Forward Flexes
  With both of your feet on the floor, and stomach held in, slowly bend forward and walk your hands down the front of your legs toward your ankles.  Hold this stretch for 15 seconds and then slowly sit back up;
   
• Neck Rolls
  With your shoulders relaxed, drop one ear to your shoulder and gently roll your neck forward and back, holding each position about five seconds.  Repeat five times;
   
• Neck Bends
  Bend your head as far back as it will go and place your hands across your forehead.  Slowly bring you head forward while resisting the movement with your hands.  This can be varied by bending your head to the right and then to the left, again resisting with your hands.  Repeat several times;
   
• Knee to Chest Bends
  Bend forward slightly.  Clasp your hands around your left knee and hug it to your chest.  Hold this stretch for 15 seconds.  Keeping your hands around the knee, slowly let it down.  Alternate legs.  Repeat 10 times;
   
• Thigh Flexes
  Make a fist with both hands and place them between your knees.  Squeeze isometrically as hard as possible for 5 seconds, then release.  Repeat;
   
• Foot Flexes
  Place your toes on the edge of your briefcase, bag or foot bar.  Thrust your heels upward, as high as possible, until you feel a maximum contraction in the calf.  Hold the contraction tightly for 2 seconds and then lower your heels as far down as possible below the edge of the bag or bar.  Repeat;
   
• Foot Extensions
  Place your heels on the edge of a briefcase, bag or foot bar.  Raise the forward part of your feet toward your shins.  Repeat in a rapid manner until the shin muscles ache;
   
• Shoulder Rotations
  Rotate your shoulders forward, then backward and finally, shrug them upward toward your ears in an "I don't know" fashion.  Repeat several times;
   
• Shoulder Rolls
  Hunch your shoulders forward, then upward, then backward, and downward, using a gentle circular motion.  Repeat numerous times.
  
  [Note:  You can view a demonstration of some of the above exercises if you have Windows Media Player or QuickTime installed on your computer.  The running time is approximately 1 minute.  The demonstration can be downloaded in 1 minute with Cable/ADSL and about 21 minutes with 56k dial up].
   

The above exercises should help you to be both more comfortable, during your flight, and to possibly avoid the rages of deep vein thrombosis [DVT].