Despite the scepticism, multiple contractors submitted bids for GEBO II, which was viewed as an influential step towards a development contract. These included Boeing, Convair, Curtiss, Douglas, Martin and North American Aviation. The majority of submissions were relatively straightforward, unambitious, and expensive. Convair, which had built the XF-92A and other delta-wing fighters, evaluated swept and semi-delta configurations, then settled on the delta wing, which offered good internal volume for support systems and fuel. It also provided low wing loading for the airframe size, permitting supersonic flight in the mid-stratosphere at . Most of the configurations studied mated the delta wing to a relatively slender fuselage housing a crew of two and powered by a pair of jet engines.