All too often, I've had trouble where the mere weight of my iPhone or MacBook power adapter is enough to pull it from its own airplane power socket. Why are they so loose? If the plug at your seat is one of the universal outlets that can accept any plug, you might find that an inexpensive Europlug adapter might have a more secure fit. I always carry one in my travel bag, even when I travel within the US. Specifically, I fly Alaska Airlines, and I always have this problem on their planes. And weirdly, the plug is recessed slightly, so the new MacBook Air Dual Charger doesn't insert fully. The adapter solves this problem as well.
Why? The Europlug may be superior. Instead of two parallel metal blades like we have used in the US since 1904, the Europlug, which came about in 1963, has two rigid pins that are slightly pointed inward, creating tension.
If you don't have a Europlug adapter, this six-pack for $6 will do the trick. Most modern phone, tablet, and laptop chargers from reputable manufacturers accept both US and overseas voltages, but check the markings on your charger to be sure. “Input: 100–240V, 50/60Hz” indicates support for both. A plug adapter changes the plug’s shape; it does not convert voltage.
If only the plugs on airplanes were mounted sideways so that the blades were horizontal... but nobody asked me.
An Alaska Airlines universal power plug, common on many airplanes.
The new MacBook Air Dual Charger doesn't work because the socket is slightly recessed.
Attach a Europlug adapter...
...and now it works and it fits more snugly!