Definition
The distance from one tip of an airfoil to the other, measured in a straight line perpendicular to the airfoil's longitudinal axis. For a wing, it is the tip-to-tip measurement; for a propeller, it is the diameter of the disk traced by the blade tips.
Plain English
How long an airfoil is from one end to the other, measured straight across.
Context Anchor
Seen in aircraft design, performance discussions, weight-and-balance data, and aircraft description charts.
Derivation
Span comes from the Old English spann, meaning the distance between two points — originally the width of an outstretched hand. In aviation it keeps that same idea: the straight-line distance from one edge to the other.
Why Pilots Care
Wing span directly influences lift, induced drag, roll rate, and structural loads.
Intuition Check
Span does not mean a length of time here. In this aviation use, span means the physical distance from one tip of the airfoil to the other.
Example Sentence 1
The Cessna 172 has a wing span of about 36 feet, which determines the minimum hangar width needed to store it.
Example Sentence 2
Increasing the span of an airfoil improves glide performance in a sailplane.