Vintage UNITED AIRLINES Pinback Button 2" Diameter metal button, 1990's-2000's era United Airlines, Inc. (commonly referred to as United) is a major American airline headquartered at Willis Tower in Chicago, Illinois. United operates a large domestic and international route network spanning cities large and small across the United States and all six continents. Measured by fleet size and the number of routes, it is the third largest airline in the world. The button is complete and in EXCELLENT condition with some overall light wear.