I called United, just for grins, and asked if a flight leaving tomorrow from NYC to London had laptop adapters installed. The agent I spoke to tried to dig this out for me, but it wasn't as easy as say, finding out what movies are playing or what my choices in special meals would be. Since I was trying for London, I next tried British Airways. They were flying a 747, and the reservation agent told me that they offered a ticket that included laptop power capabilities, but she didn't or couldn't understand what I was asking whether the equipment actually was in working order. That doesn't guarantee anything, however.
Gate agents are good at filling the plane.
I even had one ticket agent tell me 'Of course the airplane has a power adaptor. Forget the bag of peanuts. It is ironic that this is so hard. Especially for Business and First class customers, who are spending thousands of dollars of their companies' travel budgets, you would think that the airlines could really do a service here and make it easier for them to book their seats and provide the juice. Of course, I watch all of this with some amusement, since I gave up my laptop years ago.