In my single first class experience I flew Swiss F from ZRH to ORD and back on an award ticket. Naturally, since I was travelling alone, I tried to book single seats by the window (a/c was an MD11, back in 2004), but the agent on the phone told me that there were no window seats available for preassignement at the moment, so assigned me seats in the middle (D or G, I can't remember) but she said she'd make a note in the PNR that I would prefer window. When I checked in for the flight in ZRH I found I had been relocated to 3A, and when I returned from ORD I had been already put in 3K.