High Quality Content by WIKIPEDIA articles! The Hawker Siddeley P.139B was a proposed Airborne Early Warning aircraft intended to operate from aircraft carriers of the Royal Navy. The P.139B formed part of the a major equipment procurement plan for the RN in the 1960s intended to give the service a force of new, modern carriers capable of operating air groups consisting of equally new, modern and up to date aircraft. However, cuts in defence spending by the British Government in the mid 1960s meant that these proposals never came to fruition.