It is armed with torpedoes, Harpoon anti-ship missiles, and other weapons, can drop and monitor sonobuoys, and can operate in conjunction with other assets, including the Northrop Grumman MQ-4C Triton maritime surveillance unmanned aerial vehicle (UAV).

[4] In the 1980s, the USN began studies for a P-3 replacement, the range and endurance of which were reduced due to increasing weight and airframe fatigue life limitations.

[21] On 10 June 2013, a U.S. Department of Defense (DoD) Inspector General (IG) report recommended delaying full-rate production over a lack of key data to assess if the P-8 met operational requirements; additional tests were also needed to guarantee a 25-year lifespan.

[23] In 2013, full-rate production was delayed until the P-8 could demonstrate it can survive its 25-year lifespan without structural fatigue, overcome deficiencies, track surface ships, and perform primary missions.

[24] On 24 June 2013, during weapons integration testing, the P-8 achieved a milestone by firing a live AGM-84 Harpoon anti-ship missile and scored a direct hit on a low-cost modular target.

A key feature was a pod-mounted radar on the fuselage's lower centerline, positioned so the engine nacelles do not obstruct its line of sight.

[37] In the cockpit, changes were made to the flight control and alerting systems, allowing for an increased bank angle, a more responsive autothrottle, and the elimination of audible warnings during low-altitude operations.

[37] The Navy says that compared to the P-3, the P-8 has a smoother flight experience, subjecting crews to less turbulence and fumes, allowing them to concentrate better on missions.

[40] After the aircraft roll off the assembly line, five operator stations (two naval flight officers plus three enlisted Aviation Warfare Operators/naval aircrewman) are mounted in a sideways row, along the port side of the cabin.

The P-8 is to be equipped with the High-Altitude Anti-Submarine Warfare Weapon Capability (HAAWC) Air Launch Accessory (ALA), turning a Mark 54 torpedo into a glide bomb for deploying from up to 30,000 ft (9,100 m).

[44] Following the cancellation of Lockheed Martin's Aerial Common Sensor project, Boeing proposed a signals intelligence variant of the P-8 for the USN's requirement.

[53] During early exercises and the Japanese deployment, the P-8 reportedly suffered radar, sensor integration, and data transfer problems, leading to more testing.

In 2012–3, the US government's Director, Operational Test and Evaluation (DOTE) evaluated the P-8A Increment 1, and reported that it was effective for small-area and cued ASW search, localization and attack missions, but lacked the P-3C's broad-area ASW acoustic search capability; the Mk 54 torpedoes were of limited use against evasive targets.

[56] Pentagon acquisition undersecretary Frank Kendall said of the report that, although its findings are factual, it ignored future capability upgrades for ASW and surveillance.

[58] On 2 October 2015, USN P-8s stationed at Naval Air Station Jacksonville, Florida, alongside U.S. Coast Guard HC-144A Ocean Sentry, HC-130H and USAF Reserve HC-130P Combat Shadow aircraft, searched the Eastern Caribbean Sea for the missing SS El Faro cargo ship that sank on 1 October in the Category 3 Hurricane Joaquin near Crooked Island in the Bahamas.

[59] On 20 February 2018, a P-8 of Patrol Squadron Eight (VP-8) rescued three fishermen whose vessel had been adrift in the South Pacific Ocean for eight days, deploying a search and rescue (SAR) kit containing supplies and communications equipment, the first time that a P-8 deployed a SAR kit in a real operation.

[60] On 19 August 2014, a Chinese Shenyang J-11 fighter came within 30 feet (9.1 m) of a USN P-8A of VP-5 about 135 miles (217 km) east of Hainan Island while patrolling the South China Sea.

[64] In November 2016, a Russian Su-30 fighter intercepted a P-8 over the Black Sea, coming within 5 feet (1.5 m) of it, forcing the P-8 through its jet wash, causing "a 15-degree roll and violent turbulence".

[98][99][100] In April 2020, Defense Security Cooperation Agency cleared approved the sale of 10 AGM-84L Harpoon missiles along with containers, spare and repair parts, support and test equipment for the P-8I fleet to the Indian Navy at a value of $93 million.

[112] In July 2013, Air Marshal Geoff Brown, head of the RAAF, said Australia was considering buying more P-8As and fewer MQ-4C Triton UAVs than earlier planned.

[113] On 21 February 2014, Prime Minister Tony Abbott announced the intention to procure eight P-8As plus options for four more; entry into service is planned for 2021.

[114] In July 2014, negotiations commenced between Boeing and the US Department of Defense to integrate the AGM-84 Harpoon Block 1G anti-ship missile onto the P-8A on Australia's behalf.

[123] According to the Australian Defence Minister, Richard Marles, in May 2022 a Chinese J-16 is alleged to have flown alongside a RAAF P-8A, deploying flares and chaff.

[157][158] In 2013, the Defense Acquisition Program Administration (DAPA) commenced a ₩1 trillion (equivalent to ₩1.05 trillion or US$929.13 million in 2017)[159] procurement program to acquire up to 20 ASW aircraft to replace the Republic of Korea Navy's fleet of 16 P-3Cs; possible candidates included the C-295 MPA, P-8, Saab Swordfish and the SC-130J Sea Hercules.

[166] The US Department of State approved a possible Foreign Military Sale of five P-8As with associated equipment to Germany for an estimated cost of $1.77 billion.

[177] In March 2023, Canada announced the submission of a Letter of Request via the U.S. government's Foreign Military Sales program on the acquisition of up to 16 P-8As.

[182] On 23 September 2022, Boeing's Latin America director, Tim Flood, presented the capabilities of the P-8 to the Brazilian Air Force commander, General Carlos de Almeida Baptista Júnior.

According to Baptista Júnior, "the discussions have a great importance to prospect the future of FAB's maritime patrol aviation", as part of a plan to replace its P-3AMs currently in service.

[191] In 2016, Turkey indicated that it planned to acquire a new MMA aircraft to supplement existing assets, the P-8A being the main candidate based on the required performance.

[192] In December 2017, the Royal Malaysian Air Force's Brigadier General Yazid Bin Arshad announced it had shortlisted four aircraft types to replace the force's aging fleet of Beechcraft Super King Air maritime patrol aircraft; these are the EADS CASA C-295 from Airbus, the P-8 from Boeing, ATR 72 MP from ATR, and the CASA/IPTN CN-235, possibly provided by either Airbus or Indonesian Aerospace, which acquired a licence to produce it.