Quote from JW411:
"All of the British-built aircraft that I ever flew had a water humidifier system."
...as did Bergerie's VC10. Haven't checked my course notes, but I'm under the impression the water was from the aircraft's Domestic Water system? The F/Es, ever mindful of corrosion, etc., were not overly enamoured with it. Being much cleverer than us pilots, they knew that frost was building up on the inside of the fuselage skin, unseen because of the ceiling panels. Cue a massive outpouring of melt in the descent, particularly into tropical airfields - most of all into humid, sea-level airfields like Lagos - if it wasn't switched off a couple of hours before top of descent. They used the unheated portions of the cockpit side windows to gauge how much frost might be building up, and when to switch then humidifiers off.
The other idiosyncrasy of the VC10 was that the air conditioning system, in addition to having air-cycle machines for cooling the conditioned air, also had freon refrigerator packs which were used when the OAT was particularly high. In the climb, if the humidifiers were inadvertently switched on before the 'frig packs were switched off, snow would emanate from the punkah louvres.
Re punkah louvres (or fresh-air vents, as the younger generation of cabin crew insisted on calling them), I think it was Mr Boeing that first did away with them in the 1980s? Not sure about the current products off the production lines at Toulouse and Hamburg, but the louvres were still installed on the A320s through the 1990s. They're a great boon when one passenger is feeling hot, but his neighbour isn't.