Previously, Hawker Siddeley had produced a design called the HS.134 "Airbus" in 1965, an evolution of the HS.121 (formerly DH.121) Trident, which shared much of the general arrangement of the later JET3 study design.
Anteriormente Hawker Siddeley producira un deseño chamado HS.134 "Airbus" en 1965,que era unha evolución do HS.121 (anteriormente DH.121) Trident, que compartía moitas das características xerais do posterior deseño do estudio JET3.