The Grumman S-2 Tracker (previously S2F prior to 1962) was the first purpose-built, single airframe anti-submarine warfare (ASW) aircraft to enter service with the U.S. Navy. Designed and initially built by Grumman, the Tracker was of conventional design with twin engines, a high wing and tricycle undercarriage. The type was exported to a number of navies around the world. Introduced in 1952 the Tracker saw service in the USN until the mid-1970s with a few aircraft remaining in service with other air arms into the 21st century. Argentina and Brazil are the last countries to still use the Tracker.