Boeing 737

Originally developed as a narrow-body, short-to-medium range commercial jet transport aircraft, more Boeing 737 aircraft have been produced than any other commercial jet airliner. Its first version, the 737-100, went into service in 1967; it has been in incremental improvement since then, and now is in the "737 new generation", with slightly longer aircraft with extensive wing, engine, and other efficiency improvements. It is the basis for the P-8 Poseidon, developed by the U.S. Navy as a maritime patrol aircraft, and has been adapted for a variety of other military applications, such as the "Wedgetail 737" airborne warning and control system first developed for Turkey. As well as commercial passenger versions, there are civilian cargo and executive transport versions; some types are convertible between freighter and passenger configurations.

Military variants

Two significant military variants use a long-endurance airframe to carry radar, and, in the case of the P-8, additional sensors. Antenna shape and size are significant in determining the airframe configuration.

Airborne warning and control

Advances in phased array technology obviate the need for the rotating "flying saucer" radar enclosure typical of the E-2 Hawkeye and E-3 Sentry, allowing the Wedgetail 737 to use a fixed "top hat" housing for its search and track radar.

Maritime patrol

The P-8 has an the upgraded AN/APS-137D(V)5 maritime surveillance radar and signals intelligence (SIGINT) system developed by Raytheon. The system was redesignated AN/APY-10 in June 2006.

Smaller and lighter than its predecessor, the new radar is installed on the enlarged nose fairing, a lesser change than the "top hat" but still an aerodynamic effect. The aircraft is believed to be equipped, as well, Littoral Surveillance Radar System (LSRS), whose shape may be the reason the airframe was changed from a 737-700 to a 737-800, which has a longer fuselage apparently better suited for the LSRS antenna.