Memphis International Airport (IATA: MEM, ICAO: KMEM, FAA LID: MEM) is a civil-military airport seven miles (11.2 km) southeast of downtown Memphis in Shelby County, Tennessee, United States.
The Miami-Dade Aviation Department (MDAD) is an agency of the Miami-Dade County government that manages airports.
 As of 2013 Emilio T. Gonzalez is the director of the agency.
 It operates Miami International Airport, a passenger airport, and four general aviation airports.
 The other airports are Miami-Opa Locka Executive Airport, Miami Executive Airport, Miami Homestead General Aviation Airport, and Dade-Collier Training and Transition Airport.
 The executive offices are located at Miami International Airport.
The Wayne County Airport runway collision involved the collision of two Northwest Airlines planes in dense fog at Detroit Metropolitan Wayne County Airport on December 3, 1990.
 It occurred when Flight 1482, a scheduled Douglas DC-9-14 operating from Detroit to Pittsburgh International Airport, taxied onto an active runway by mistake in dense fog and was hit by a departing Boeing 727 operating as Flight 299 to Memphis International Airport.
 One crew and seven occupants of the DC-9 were killed.
Bishop International Airport (IATA: FNT, ICAO: KFNT, FAA LID: FNT) is a commercial and general aviation airport located in Flint, Michigan.
 It is named after banker and General Motors board member Arthur Giles Bishop (April 12, 1851 – January 22, 1944), who donated 220 acres of his farmland for the airport in 1928.
 The third busiest airport in Michigan, it surpassed competitor MBS International Airport in terms of airline operations in 2002.
 In 2007, 1,071,238 passengers used Bishop International Airport; in 2011, 938,914 passengers used the airport.
 It is included in the Federal Aviation Administration (FAA) National Plan of Integrated Airport Systems for 2017–2021, in which it is categorized as a small hub primary commercial service facility.
 The airport is currently served by several passenger airlines: Allegiant Air, Southwest Airlines and Delta Air Lines operate mainline service out of the airport, as well as affiliates of Delta Connection, United Express and American Eagle.
 Additionally, FedEx Express and a FedEx Feeder affiliate operate cargo services out of the airport.
 Accompanying the airlines is fixed-base operator Av Flight that handles both general aviation and airline operations and the flight school American Wings Aviation.
 Bishop International Airport is in southwestern Flint, and is surrounded by Flint Township to the north, east and west; and Mundy Township to the south.
FedEx Express Flight 1406 was a cargo flight from Memphis International Airport, Memphis, Tennessee, to Logan International Airport in Boston, Massachusetts, when it suffered a cargo fire in-flight over New York.
 The three crew members on board successfully made an emergency landing at Stewart International Airport, New Windsor.
 After the evacuation, the DC-10 was consumed by fire.
 After extensive investigation, the National Transportation Safety Board was unable to determine what caused the fire.
 Nevertheless, the Federal Aviation Administration made recommendations to prevent similar incidents from occurring in the future.
San Martin Airport (formerly "South County Airport of Santa Clara County", colloquially "South County Airport") (FAA LID: E16) (formerly Q99) is a public non-towered airport located one mile (1.6 km) east of San Martin, serving Santa Clara County, California, U.S.A. This general aviation airport covers 179 acres (72 ha) and has one runway.
 A self-service fueling facility offers 100LL aviation gasoline continuously.
 Jet-A fuel is available from a full-service truck during FBO operating hours, and major airframe and powerplant service are available.
 The FBO at South County, which serves Jet-A and 100LL is Magnum Aviation.
Harford County Airport (FAA LID: 0W3) is a public airport located in the City of Churchville, in Harford County, Maryland, USA.
 Harford County Airport is a general aviation (GA) airport in northern Maryland that serves primarily recreational pilots.
 There are three runways at Harford, two grass/turf and one paved.
 The popular runway in the summer time is the grass runway 01/19.
 However, in November, the turf is closed as the grass generally remains wet and soggy over the winter months.
 The diagonal turf runway 14/32 is rarely used by powered pilots except during high crosswind conditions.
 The prevailing winds generally vary between favoring 28 and 19.
 The airport has a large sailplane/glider contingent and is home of the Atlantic Soaring Club.
 The airport serves some commercial activities, mainly sight seeing and flight training (through Harford Air Services) as well as biplane rides and hot air balloons (run by Light Flight Balloons www.fun-flying.com).
 In the Spring of 2012 a Skydiving company, Skydive Baltimore, moved their operations from Ridgley and started operations at the airport.
Sheridan County Airport (IATA: SHR, ICAO: KSHR, FAA LID: SHR) is a county owned, public use airport in Sheridan County, Wyoming, United States.
 It is located two nautical miles (4 km) southwest of the central business district of Sheridan, Wyoming.
 The airport is mainly used for general aviation.
Rumbula (ICAO: EVRC) is an air base located 11 km southeast of Riga city centre in Latvia.
 The airfield had military use in the 1950s and 1960s.
 In the 1960s it was used as temporary passenger airport for bigger planes until the new Riga International Airport was opened in 1973.
 At least since 2001 there has been no military or commercial aviation based in Rumbula.
 Now it is mainly used as the biggest auto market in Latvia, and only about five small general aviation planes are based here.
 The runway is in very poor condition, with holes and concrete blocks often used to learn how to drive a car or for "test drives" of cars to be sold at the market.
 It is difficult to find a continuous whole and obstacle-free piece of the runway which is more than 3000m long.
 There are also a few "bomb-proof" camouflaged military hangars (one example is located at 56°53'08.39" N / 24°13'33.93" E).
 The hangars are mainly used as storage or general purpose facilities; they are not obvious on satellite images and are not freely accessible on the ground.
The United States has an extensive air transportation network.
 In 2013 there were 86 airports in the U.S. that annually handled over 1,000,000 passengers and twelve of the world's thirty busiest airports by passenger volume in 2014 were in the U.S. (down from 17 in 2004), including the world's busiest, Hartsfield-Jackson Atlanta International Airport.
 In 2012 88% of all traffic was through the 62 busiest airports in the country.
 In terms of cargo, in 2015, eight of the world's thirty busiest airports were in the U.S., including the world's second busiest, Memphis International Airport.
 Private aircraft are also used for medical emergencies, government agencies, large businesses, and individuals, see general aviation.

Question: Which airport is mainly used for general aviation, Memphis International Airport or Sheridan County Airport?
Answer: Sheridan County Airport