SEATTLE The global commercial aviation fleet will stand just under 50,000 planes in 2044, with most built over the next 20 years, according to a Boeing forecast. The global fleet will nearly double to 49,600, a bit below Boeing's prior annual outlook, the company said ahead of the giant Paris Air Show which began today. Emerging markets "with expanding middle classes, dynamic and competitive airline networks and sustained aviation investment" will represent more than 50 percent of the