In the last three years, I've traveled quite a bit internationally and have seen laptops get really abused and misused going through security checkpoints. Travelers are asked to take their computers out of their carry-on luggage and out of their computer bags/covers. After that, the laptop is fair game to be picked up, bumped, tossed down hard and hopefully make it to the other side of the screening process in one piece. In the rush to get all their belongings (shoes, keys, coins, belts, coats, purses and more) the poor laptop owner often rams it back into the laptop bag with little regard for it's protection. The worst airport for carry-on luggage/laptop abuse I've seen is the airport in Rome, Italy whereas Amsterdam security treats personal property more kindly.
A laptop sleeve gives protection when the computer is taken out for inspection and would help soften some of the blows the laptop is subjected to before it's safe return, nestled in it's bag. The laptop sleeve gives protection while it's being used on the airplane too. Many times I've seen computers left on the seat while the passenger steps to the back of the plane and someone else gets out of the same row and the computer gets bumped against the armrest. The sleeves fit snugly, come in a large selection of sizes, are lightweight and very affordable. Protection from liquid spills (haven't been on a fight yet that hasn't experienced some turbulence) is also very important.
On of the best laptop accessories for a traveler is a set of headphones. With a large selection of brands and prices from an entry level set to a Bose system, there is a set to meet everyone needs. Headphones, earbuds (some are made of gel), with wire or wireless, clip-ons and noise-cancelling-in-ear sets , help the user block out outside noises whether in an airplane or in a terminal. It also keeps others from hearing what the user is doing.
Backpacks and cases also come is a wide range or sizes, brands and price. An unusual backpack is the Built NY Laptop Backpack Med-Olive - E-BPM-OLV which looks like a vest and is worn snugly against the body. International adapters and power surge protection is vital while traveling as many foreign counties wire electricity differently than the U.S. and it's easy to "fry" a laptop if caution is not taken. Before taking a trip, a little planning for a laptop goes a long way to ensure the safety of a computer.