DALLAS (AP) — United Airlines, which lost the distinction of being the world's biggest carrier after shrinking for several years, plans to regain lost ground by adding more flights from key airports this summer. The airline wants to upgrade facilities at key airports and trim the use of smaller planes on important business routes. If the expansion plans pan out, United could staunch slipping revenue numbers, which fell nearly 2 percent in the last five years, while revenue at industry leader Delta Air Lines Inc.Read more on NewsOK.com