A powerful-looking swift with long saber-shaped wings and a bullet-shaped body. The only swift in its range that combines a clean white throat and smooth pale gray back. At close range, the fine white forehead and bluish tinge to the back are also visible. Flies higher than most other swifts during migration, often circling over mountaintops and valleys with kettles of migrating birds of prey. Less erratic and bat-like in flight than other swifts. Call is a high-pitched, screaming twitter.