Why does airline food taste bland?

Because your sense of taste genuinely changes at altitude. The food is usually seasoned more heavily than restaurant food, not less — you simply cannot taste it properly.

Three things happen in a pressurised cabin at cruising altitude.

The air is extremely dry. Cabin humidity typically sits around 10–20%, drier than most deserts. Dry nasal passages cannot detect aroma well, and since most of what we call flavour is actually smell, that alone removes a large part of the experience.

The cabin is pressurised to the equivalent of around 6,000–8,000 feet, not sea level. Reduced pressure dulls the taste buds directly. Research commissioned by airlines has found that perception of sweet and salty drops by around 30% under these conditions.

Noise matters too. Studies have shown that loud background noise — a cabin runs at 80–85 decibels — further suppresses sweetness perception while, oddly, slightly enhancing umami.

That last finding explains one of the strangest facts in aviation catering: tomato juice. It is ordered far more often in the air than on the ground, because tomato juice is umami-rich and its earthy quality reads as pleasant at altitude where it can taste flat on the ground.

Airlines respond by over-seasoning, leaning on umami-heavy ingredients, and increasingly by designing menus tested in pressurised chambers.

There are practical constraints too. Food is cooked on the ground, chilled, then reheated in convection ovens, which suits braises and pasta and destroys anything meant to be crisp or rare.

Staying hydrated helps a little, since some of the effect is your own dryness rather than the food's.