Long distance, well, very long distance flights keep you in the same area of exchanged breaths for many hours. A shower would be nice. There are two airlines that offer in-flight showers both using the same aircraft: the A380. But before you get excited, you need to be a first class passenger and both companies operate from the United Arab Emirates 9where the real money is, you say).
Yes, Etihad Airways and Emirates Airline offer showers to their select passengers but with Etihad it is one shower to the fourteen first class passengers so when busy, booking it is essential, especially as up to half an hour is allowed in the shower even though the hot water may only hold up for five minutes.
You can book these luxury flights from other companies but you get onto these two airlines only. Not in first class? Forget a shower. It won't happen.