Indonesian Air Force Foundation Day is observed in Indonesia every April 9. This day commemorates the establishment of the Indonesian Air Force (Tentara Nasional Indonesia-Angkatan Udara), which was officially formed on April 9, 1946. The foundation of the air force marked a significant development in Indonesia's military history, following its independence and the end of the Indonesian National Revolution. The air force played a crucial role during the revolution, utilizing aircraft left by the Japanese and the Dutch. Today, the Indonesian Air Force is one of the strongest in Southeast Asia, with nearly 38,000 personnel and over 220 aircraft, including notable models like the Su-27 and F-16 Fighting Falcon. Celebrations typically include ceremonies and events that honor the contributions of the air force in maintaining national sovereignty and security.