The partnership would have been unthinkable a few years ago. Sukhoi, the Soviet maker of military planes, and Gulfstream, the most prestigious name in U.S. corporate jets, are making tentative plans to build a supersonic business aircraft. In a $1 billion project, the two manufacturers hope to produce a jet that will fly at 1,500 m.p.h., twice the speed of sound, and carry as many as 20 passengers over a range of more than 5,600 miles. The plane would sell for about $50 million.
The project is still in the design stage and faces abundant obstacles, including concerns about the effect...