Ergonomics specialist website, The Ergonomenon, points out three specific causes of physiological stressors while flying and working from a laptop:
1. The monitor and keyboard are attached. This means you are forced to crane your neck down to see the monitor rather than keep a neutral position
2. The keyboard is too small, causing the elbows and forearms to pronate inward at an unnatural angle
3. Laptops do not have adequate cooling systems. Hot laptop batteries have been known to cause burns and studies indicate that men who frequently use laptops directly on their laps risk lower sperm counts and infertility
1. Don't Hunch: Before using a laptop angle the laptop so the neck remains in a relaxed and neutral neutral position, aiming to align screen with eye level. One of the most affordable, light, and airline-friendly designs is the appropriately named, Aviator Laptop Stand. Just 8 oz and the setup breaks down into 3 parts for easy stow away; $19.99. If traveling without such a stand, using a pile of books or magazines to raise viewing angle closer to the eyes. Every degree helps.
A compact travel-sized mouse like the Microsoft Arc can help unshackle you from using the less ergonomic touchpad on a laptop.
2. Accessorize for Comfort: Switching to an external keyboard and mouse helps ease the stress of tightly positioning arms into an unnatural position. Consider purchasing a small travel mouse and/or wireless keyboard (wireless Bluetooth keyboards are useful dual-device peripherals which can switch between laptop and tablets).
3. Keep the Laptop Off Your Lap: regardless of what they're called, working with a laptop on the lap is only recommended for short stints, as user posture suffers greatly when the head, neck, and shoulders are required to hunch down and forward. The Ergonomenon recommends a laptop stand with a built-in fan/cooler (just note this will require plugging into a USB port for power and drain the laptop battery faster than without it). My personal favorite is the affordable Targus Chill Mat, which is keeping the MacBook Pro cool ever since I purchased one over a year ago.
And remember to stop every half hour and get up to stretch those muscles! Staying productive on a plane is not as important as remaining healthy, so listen to your body, and regularly put away the laptop and give those keyboard pounding fingers a rest.