An unidentified South Korean military source told The Korea Herald that the new planes would augment the country's fleet of Lockheed Martin P-3 Orions and enhance South Korea's surveillance capabilities of North Korea.
"The Defense Acquisition Program Administration is currently working on a plan, which is likely to be an overseas purchase program," the source said.
The budget for the project, the newspaper said, is an estimated $889 million.
The reported approval of the plan by South Korea's Joint Chiefs of Staff couldn't be immediately confirmed.
Boeing, with its new P-8 Poseidon, is a possible candidate to provide new maritime patrol aircraft. So are Lockheed Martin and its SC-130J Hercules and Airbus Military's C-295 MPA, the official was quoted as saying.
The South Korean navy is in the process of modernizing its 16 P-3s with new sensors and radars. The upgrades are expected to be completed by 2016.