En route, ask for bottled or canned water when the bar cart comes by. I definitely do not recommend petroleum jelly or creams. It smells nice. Jojoba oil is also good and a little thicker. Immerse entirely, even and especially your head.
Bathing when dehydrated helps to replenish moisture right through the pores.
Bathing also relaxes the nervous system. Somewhere between New York and Buenos Aires my nose started to bleed. Since I never had nose bleeds, I knew it had to be from the dryness of the cabin air. Now I am planning a return trip.