For the past couple of months, locals and visitors to Wellington, New Zealand, have been reminded of the country’s pending purchase of new airlifters—formally called the Future Air Mobility Capability (FAMC) Project—by billboards in the city and at its airport. Touting Embraer’s offering, they read “KC-390, The True First Responder.” Embraer is among a quartet of manufacturers vying to replace New Zealand’s aging fleet of five Lockheed C-130H ...