How many letters does the top answer for “artillery designed to shoot upward at airplanes” have?

The most common answer is antiaircraft (12 letters).

Crossword clue: artillery designed to shoot upward at airplanes

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

antiaircraft 12 letters wn-def

artillery designed to shoot upward at airplanes

flack 5 letters wn-def

artillery designed to shoot upward at airplanes

flak 4 letters wn-def

artillery designed to shoot upward at airplanes