United Airlines is the largest airline in the world; it has the leading number of destinations in the whole world. It avails air services for 1000 destinations in 170 countries and about 700 aircrafts are functioned by it. It comes with a strong global route network and 10 global hubs.
Headquartered in Atlanta, Georgia and United States, Delta Airlines is a major American Airline company. It avails air services for all continents except Antarctica. Delta and its companies run about 5000 flights on daily basis. About 80,000 work for this airline.
Headquartered in Burlingame, California, Virgin America flies to 20 destinations within the country and three destinations in Mexico. This also comes with code share agreements with Hawaiian Airlines, Singapore Airlines China Eastern Airlines and Virgin Australia. The airline's fleet of 55 aircraft includes totally to Airbus planes.