Boeing has introduced the third and last dedicated flight test aircraft for the P-8A anti-submarine warfare and maritime patrol programme.
The aircraft named T3 - a mission systems and weapons testing aircraft - completed its first flight test on 29 July at Boeing Field in Seattle, Washington.
T3 in a few weeks will join the first two flight test aircraft currently based at NAS Patuxent River, Maryland.
Boeing has spent the last 10 months modifying T3 with mission systems after completing first flight on 23 September.
The P-8A test fleet includes two aircraft - S1 and S2 - for static and fatigue evaluations.
The US Navy plans to buy 117 P-8As to partly replace about 230 Lockheed Martin P-3C Orions over the next 10 years. The P-3C also is being replaced by a new Broad Area Maritime Surveillance fleet, with the Northrop Grumman RQ-4N unmanned aircraft system as the selected platform.
The Indian navy, meanwhile, has placed an order for the P-8I, which will also include an aft-mounted radar for 360º coverage and an air-to-air tracking mode. Boeing completed final design review for the P-8I on 16 July.