United Airlines is one of the major  airlines based in the United States. It is a subsidiary of United Airlines  Holdings and operates a large domestic and international network, serving  destinations across the Americas, Europe, Asia, Africa, and Oceania. Here are  some key points about United Airlines:
  
    - History:  United Airlines was founded in 1926 and has a rich history in aviation. It has  gone through various mergers and acquisitions over the years, including the  merger with Continental Airlines in 2010.
- Hub  Airports: United Airlines has several hub airports in the United States,  including Chicago O'Hare International Airport (ORD), Denver International  Airport (DEN), George Bush Intercontinental Airport in Houston (IAH), Los  Angeles International Airport (LAX), Newark Liberty International Airport  (EWR), and San Francisco International Airport (SFO).
- Fleet:  United Airlines operates a diverse fleet of aircraft, including planes from  both Boeing and Airbus. Its fleet includes models such as the Boeing 737, 757,  767, 777, and 787, as well as the Airbus A319, A320, A350, and others.
- MileagePlus:  United Airlines has a frequent flyer program called MileagePlus, which allows  passengers to earn and redeem miles for flights, upgrades, and other benefits.  The program offers different elite status levels based on the number of miles  flown with United and its partner airlines.
- Alliances  and Partnerships: United Airlines is a member of the Star Alliance, which is  one of the largest airline alliances in the world. This partnership allows  United to offer passengers access to a vast network of destinations and  seamless connections with other member airlines.
- Services  and Amenities: United Airlines offers various services and amenities to enhance  the travel experience for its passengers. This includes different cabin  classes, such as United Polaris Business Class and United Premium Plus, as well  as amenities like in-flight entertainment, Wi-Fi on select aircraft, and  complimentary meals and beverages on longer flights.
- Corporate  Social Responsibility: United Airlines has initiatives focused on environmental  sustainability, community engagement, and diversity and inclusion. The airline  has set goals to reduce its carbon emissions, invest in sustainable aviation  fuel, and support various social and community programs.
 
  It's important to note that specific  details about United Airlines, such as routes, policies, and services, may  change over time. For the most up-to-date and accurate information, it's  recommended to visit United Airlines' official website or contact their  customer service directly.