Abstract: A turbofan engine is provided with a conventional air by-pass duct communicating with a plenum chamber downstream of the engine core, vectoring nozzles upstream of the by-pass duct, and a non-vectoring nozzle and a jet-pipe exhausting from the plenum chamber. In conventional forward thrust mode the two sets of nozzles are closed and the jet-pipe is open. In lift thrust mode the jet-pipe is closed and the two sets of nozzles are open, the non-vectoring nozzle providing vertical thrust. The closure member for the vectoring nozzle is arranged, when open, to divert turbofan air to the vectoring nozzles which would otherwise have passed along the by-pass duct, and to divert to the vectoring nozzles exhaust gases from the plenum chamber that are constrained to flow in reverse along the by-pass duct. The non-vectoring nozzle is sized to permit a suitable split between gases exhausting there through and gases reverse flowing along the by-pass duct.