Boeing Y1B-9 from the left
Here we see the Boeing Y1B-9, an early monoplane bomber of 1930-31 that only reached pre-production status. However some of the lessons learnt on the B-9 helped with the development of the B-17 Flying Fortress.
How to cite this article:
Rickard, J (7 April 2019), Boeing Y1B-9 from the left , http://www.historyofwar.org/Pictures/pictures_B-9_landed.html