Dogfight

Executives of Bombardier Aerospace seemed a bit defensive when they traveled from their Montreal headquarters to a recent aviation fair in So Paulo. Just east of Brazil's business capital are the headquarters of Embraer, Bombardier's smaller but aggressive rival. The two companies had fought for a decade over the burgeoning global market for regional jets — the ones with 20 to 100 seats that fly routes like Frankfurt to Munich. But at the So Paulo show, Embraer opened a new front in the battle, flaunting its first executive jet, the attractively priced $20 million Legacy.

"There is really...