They must use more aromatic seasonings than normal because food tastes blander in an airplane than on the ground. First, the cabin pressure decreases the volatility of the odorant molecules and therefore the passenger's capability of sensing them. Second, the cabin's relatively dry atmosphere dehydrates and therefore impairs the passenger's olfactory sensory mechanism.
The cabin's low humidity also dehydrates the passenger's entire body. Consequently, the chef should not season liberally with salt because it would increase the body's need for water. Many passengers compound the dehydration problem by consuming quantities of coffee and alcohol (both diuretics), canned tomato juice (extremely salty), and soft drinks laden with thirst-producing sugar. The one liquid that would do them the most good is plain water, which they seldom imbibe on planes.
** Asian Recipes