Thanks for the info everyone.
The kind of use I imagined is best described by a couple of posts relating to aircraft such as the RAF TriStar and Nimrod. Unlike a commercial airliner I imagine they spend a fair amount of time waiting on the deck in a more humid environment than at
36, 000ft. So I suppose that there are no airlines that dehumidify on the ground for reliability reasons.
The question is does it actually make the Nimrods or Tristars more reliable in practice? Less liable to avionics problems on start-up? Carl, any views?