[1] In the mid-1980s, the U.S. Navy made plans to replace the large number of Lockheed P-3 aircraft which would reach the end of their useful service lives during the 1990s.

However, the U.S. Navy was unwilling to select Lockheed's P-3G without any competition and issued the final "Request for Proposals (RFP)" in January 1987.

However, in November 1989, Lockheed announced a cost overrun of $300 million due to the tight schedule and design problems.

The wing center section was increased in length, which moved the engines farther away from the fuselage to reduce noise levels in the cabin.

The primary submarine detection sensor was to be the sonobuoy, of which 112 were carried internally; 38 more could be stowed for in flight reloading.