|This spell grants to the caster the ability to fly through the air.|
Flight is a level 3 Charms/Air Magic spell which causes the caster to fly for its duration. Unlike some sources of flying, you may cast Flight at any time during its duration to extend it. The higher your spell power, the longer your flight will last.
Flight is generally a useful spell to have, particularly in waterlogged branches such as the Swamp, the Shoals, the Abyss, and Cocytus. Exploration of those areas is much easier when you aren't splashing around in shallow water or forced to find a way past deep water and lava. It also makes many smaller treasure vaults accessible, or at least much more convenient to reach.
It is a spell that most characters will eventually have some use for, and requires the exact same skills at the same level necessary to cast Repel Missiles, another universally desirable spell. Unless you already have flight available from another source (boots of flight, a ring of flight, a large stack of potions of flight, or innate flying ability), it's almost always worthwhile learning this.
Unlike most status effects, flight does not immediately get dispelled after you are struck by a Quicksilver Bolt. This is done in order to avoid infuriating sudden deaths. Even so, you only have one turn after being blasted to get to safety - if walking a single space away won't get the job done, consider reading a scroll of blink to do so, or refreshing your flight by casting the spell again.
Flight was removed in 0.17.