The 3-1-1 rule costs more people their sunscreen than any other item at security. Here is exactly what size you can carry on, what counts as a liquid, what the checked-bag limits are for aerosols, and how to arrive with SPF that still works.

Flying somewhere hot in December or January? Your skin has spent months out of the sun and the UV where you are landing is far stronger than at home. Here is how to pack, prep, and tan without ruining day one.