How many letters does the top answer for “linear distance between the extremities of an airfoil” have?

The most common answer is wingspan (8 letters).

Crossword clue: linear distance between the extremities of an airfoil

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

wingspan 8 letters wn-def

linear distance between the extremities of an airfoil

wingspread 10 letters wn-def

linear distance between the extremities of an airfoil