All other conditions being the same, air travel has two physical aspects different from other modes of travel.
The air in the cabin is dryerdrier. This is why you are encouraged to drink water during your flight. Why would this promote sweating? The moisture in your skin would evaporate and your body is trying to compensate.
The pressure in the cabin might be lower than the atmosphere at ground level, which would increase the evaporation rate on your exposed skin.