When traveling, I highly recommend bringing along a power strip or a power cube. Yes, we all travel with lots of electronics so this device comes in handy but there are other reasons as well. I use a Monster Outlets To Go Power Strip and its companion option with a USB port in it. The reason I like this device is that it is small, but it also has a power indicator in it. The rear of the male plug glows blue when there is power. In hotel rooms you would be surprised how much this simple feature helps.
The reason I like the power cube or Triple Outlet Adapter is that it helps to offset transformers that cover more than one outlet.
Another thing to consider is that the airplane in seat power outlets often times have a spring switch that needs to be despressed to provide power. I have been very unsuccessful with the typical USB power adapters as they are very light and get pushed out easily. Using the power strip or cube to provide additional mass has helped to keep the switch engaged.