The Hawker Siddeley P.1154 was a planned supersonic vertical/short take-off and landing (V/STOL) fighter aircraft designed by Hawker Siddeley Aviation (HSA). Development originally started under P.1150, which was essentially a larger and faster version of the basic layout and technology being developed by the smaller subsonic Hawker Siddeley P.1127/Kestrel. A key difference of this design was the addition of plenum chamber burning, essentially an afterburner-like arrangement in the thrusters used during hover, greatly increasing their thrust.