With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: Great confidence was placed in being able to reduce the noise of a turbojet and massive strides by SNECMA in silencer design were reported during the programme. However, by 1974 the spade silencers which projected into the exhaust were reported to be ineffective. The Olympus Mk.622 with reduced jet velocity was proposed to reduce the noise but it has yet to be developed.
text_B: Has the Olympus Mk. 622 completed development?
NO.