The first time the US Navy studied the use of Constellation aircraft as airborne early warning aircraft was in 1949. The first PO-1W designated airborne early warning Constellation was equipped with long range radars, which were mounted on the top and below the fuselage was first flown on 9th June 1949. The EC-121 Warning Star was first introduced in the year 1954 and was in service until 1978, only a single Electronic Warfare variant remained in active service with the United States Navy, it was retired in 1982.