Question: What airline operates United Club as well as a regional airline?

Context paragraphs:
SkyWest Airlines: SkyWest Airlines is a North American airline owned by SkyWest, Inc. and headquartered in St. George, Utah, U.S..  According to the Airlines for America definitions, SkyWest is a North American major airline.  SkyWest however, operates on a regional airline level and is a member of the Regional Airline Association.  SkyWest Airlines flies to 238 cities, in 45 states; Washington, D.C., six Canadian provinces and five cities in Mexico.  The airline serves as a feeder airline, operating under contract with various major carriers.  It flies as SkyWest Airlines in a partnership with Alaska Airlines, as United Express on behalf of United Airlines, as American Eagle on behalf of American Airlines, and as Delta Connection on behalf of Delta Air Lines.  SkyWest also provides ground handling services for airports across the United States.

Cathay Dragon: Hong Kong Dragon Airlines Ltd (Chinese: 港龍航空公司), operating brand as Cathay Dragon (Chinese: 國泰港龍航空) and previously as Dragonair, is a Hong Kong-based international regional airline, with its corporate headquarters, Cathay Dragon House, and main hub at Hong Kong International Airport.  As of 30 October 2013, the airline operates a scheduled passenger network to 44 destinations in 13 countries and territories across Asia.  Additionally, the airline has 3 codeshares on routes which are served by partner airlines.  It has an all Airbus fleet of 41 aircraft, consisting of A320s, A321s and A330s. Cathay Dragon is a wholly owned subsidiary of Hong Kong's flag carrier, Cathay Pacific, and is an affiliate member of the Oneworld airline alliance.  The airline was founded on May 24, 1985 by Chao Kuang Piu, the airline's present honorary chairman.  Its maiden flight departed Hong Kong for Kota Kinabalu, Malaysia after being granted an air operator's certificate (AOC) by the Hong Kong Government in July 1985.  In 2010, Dragonair, together with its parent, Cathay Pacific, operated over 138,000 flights, carried nearly 27 million passengers and over 1.80 billion kg of cargo and mail.

Regional airline: Regional airlines are airlines that operate regional aircraft to provide passenger air service to communities without sufficient demand to attract mainline service.  There are two main ways for a regional airline to do business:

Punto Azul: Punto Azul is a regional airline based in Malabo, Equatorial Guinea.  Its main HUB base is Malabo International Airport.  The airline operates scheduled flights mainly from the thriving Capital of Malabo, private charters for oil and gas industry of Equatorial Guinea and cargo.

Regional Airline Association: The Regional Airline Association (RAA) is a business association founded in 1975 that represents 31 North American regional airlines and 280 associate, non-airline members.  This includes manufacturers of products and services supporting the regional airline industry.  The RAA is the collective bargaining voice for its members' interests and lobbies on their behalf before the United States Congress, Department of Transportation, Federal Aviation Administration and other federal agencies.  The RAA represents the financial and economic interests of regional airline employers and regional airline support industry employers.  The Regional Airline Association does not represent financial or economic interest of airline employees, either union or other.  The RAA is headquartered in Washington DC.

United Club: United Club is the airport lounge associated with United Airlines as well as its regional affiliates.

Air Wisconsin: Air Wisconsin Airlines is a regional airline based at Appleton International Airport in the town of Greenville, Wisconsin, United States, near Appleton.  Air Wisconsin is the largest privately held regional airline in the United States.  It currently operates regional jet flights as American Eagle under contract to American Airlines via a code sharing agreement, serving cities in the U.S. and Canada with hubs at Boston Logan International Airport (BOS), Charlotte Douglas International Airport (CLT), Philadelphia International Airport (PHL) and Ronald Reagan Washington National Airport (DCA) .  Air Wisconsin previously operated United Express service on behalf of United Airlines followed by US Airways Express service on behalf of US Airways prior to becoming an American Eagle regional air carrier.  The company has announced it will once again partner with United Airlines as a United Express code sharing air carrier with primary hubs to be located at Chicago O'Hare International Airport (ORD) and Washington Dulles International Airport (IAD) beginning in September 2017 and will be "exclusively operating" as United Express by March 2018.

Penobscot Island Air: Penobscot Island Air is a small regional airline based at Knox County Regional Airport, Maine, United States (RKD) operating from a private terminal.  The airline operates scheduled service to the islands in Maine's Penobscot Bay, and offers private charter land and seaplane flights throughout the region.

Air Costa: Air Costa was an Indian regional airline headquartered in Vijayawada and based out of Chennai Airport.  It was owned by Indian business company LEPL Group.  The airline commenced operations as a regional airline in October 2013 using two Embraer E-170 aircraft with the first flight taking off from Chennai on 16 October 2013.  The airline got a permit for pan India operations in October 2016.  The airline focused on connectivity between tier II and tier III cities in the country and invested as of 2015.  Air Costa operated 32 daily flights to nine destinations from its focus cities Chennai and Vijayawada as of 2015.  The airline had a maintenance center in Chennai.  On 28 February 2017, it suspended operations until further notice.

TAP Express: TAP Express (Transportes Aéreos Portugueses or TAP for short) is a Portuguese regional airline brand name for TAP Portugal which operate short- and medium-haul routes.  TAP Portugal's lone wholly owned regional airline, Portugália Airlines, operates under the TAP Express banner.  White Airways, an airline owned by Omni Aviation, also operates regular flights for TAP Express using 9 ATR 72 turboprops.  Its head office is on the grounds of Lisbon Portela Airport in Lisbon.

Supporting paragraphs: United Club Regional airline
Answer: United Airlines