Gloster Meteor F8 "Prone Pilot"

A heavily modified Gloster Meteor F8 fighter, the "prone position/prone pilot" Meteor, was used by the Royal Air Force in 1954 and 1955 to evaluate the effects of acceleration/inertia-induced forces while flying in a prone position. Along with the Reid and Sigrist R.S.4 "Bobsleigh", the Gloster Meteor was engaged in a proof-of-concept experimental programme that proved in practice that the difficulties in rearward visibility and ejection outweighed the advantages of sustaining higher g effects.

Source: Wikipedia — Gloster Meteor F8 "Prone Pilot" (CC BY-SA 4.0)