Definition
Vertical air currents in which a body of air is moving upward (updraft) or downward (downdraft) relative to the surrounding atmosphere. In turbulent conditions near the ground, these currents can rapidly change an airplane's altitude, airspeed, and angle of attack, requiring active control inputs during approach and landing.
Plain English
Pockets of rising or sinking air. An updraft pushes the airplane up; a downdraft pulls it down. They often come in quick succession in turbulent air and disturb the airplane's flight path.
Context Anchor
Encountered during approaches and landings in turbulent air, especially near terrain, trees, buildings, or uneven heating from the ground.
Derivation
Draft' here comes from the older sense of a current of air drawn through a space (same root as a 'draft' through an open window). 'Up' and 'down' simply mark the direction the air is moving. Knowing this helps the pilot picture air as something that flows vertically, not just horizontally.
Why Pilots Care
These currents can cause rapid altitude loss or gain near the ground, requiring immediate pitch and power adjustments to maintain a stable approach path.
Grounding Statement
Imagine flying over a sun-baked parking lot next to a shaded field on a hot afternoon: the air rises sharply over the hot pavement and sinks over the cool grass, bumping the airplane up and then down as you pass over each.
Intuition Check
Do not read draft here as a rough written copy. In this context, a draft is moving air, and up and down drafts are vertical air movements.
Example Sentence 1
On short final, the pilot added a small amount of power to compensate for a downdraft that briefly sank the airplane below the glidepath.
Example Sentence 2
A strong downdraft just before the runway threshold forced the pilot to apply full power to arrest the sudden sink rate.