Balloon busters were military pilots known for destroying enemy observation balloons. These pilots were noted for their fearlessness. Seventy-seven flying aces in World War I were each credited with destroying five or more balloons, and thus were balloon aces (See list below). It was not until special Pomeroy incendiary bullets and Buckingham flat-nosed .45 calibre explosive bullets became available on the Western Front in 1917 that any consistent degree of success was achieved. Le Prieur rockets were withdrawn from service in 1918 once incendiary bullets had become available.