The U.S. Navy Lockheed YP3V-1 <i>Orion</i> prototype (BuNo 148276) in flight. This aircraft was the third Lockheed <i>Electra</i> airliner modified as an aerodynamic prototype for the P3V. It made it s first flight on 25 November 1959 and was redesignated YP-3A in 1962. The first pre-production P3V-1 (P-3A) flew on 15 April 1961.
U.S. Navy
<a rel="nofollow" class="external text" href="http://www.navy.mil/ah_online/department_arch.html">U.S. Navy All Hands magazine</a> <a rel="nofollow" class="external text" href="http://www.navy.mil/ah_online/archpdf/ah196104.pdf">April 1961</a>, p. 41.