From Longman Dictionary of Contemporary EnglishV-formationV-for‧ma‧tion /ˈviː fɔːˌmeɪʃən $ -fɔːr-/ noun [countable] CFif birds or planes fly in a V-formation, they form the shape of the letter V as they fly
Examples from the Corpus
V-formation• Highly gregarious, and collectively noisy, they fly fast and direct, but often with rather laboured wing-beats and in V-formation. 