I have posted this before and made Don Hoey, roll with laughter. I'll post again
Temperature and humidity are both low in a jet aeroplane hold and anything in there for a period of time such as a long haul flight will be very cold. I have been advised to wrap camera gear in a sealled poly back. Upon arrival at your destination the gear will be protected from any condensation as air trapped inside should be fairly dry at least equal to home humidity but any local humidity forming on the cold bag allows camera gear to remain dry until the bag has equlaised after a few hours.
I remember when I worked in Thailand my laptop, required for the job was always wet on arrival to site as my accomocation was air conditioned and site was not initially, as soon as site became airconditioned the problem disappeared. Worrying to see a computer with moisture all over but it did not long term damage.
Sorry if this does not really answer the question but I though I would share again...and possibily get another laugh!