Question: Grand Canyon Scenic Airlines operates sightseeing flights from an airport in what county?

Context paragraphs:
Air Vegas: Air Vegas (IATA: 6V, ICAO: VGA, Call sign: Air Vegas) was an airline with its headquarters on the grounds of the North Las Vegas Air Terminal in North Las Vegas, Nevada.  It operated daily sightseeing flights from Las Vegas to the Grand Canyon.  Prior to moving to the North Las Vegas Airport its main bases were McCarran International Airport (LAS), Las Vegas and Henderson Executive Airport (HND), Las Vegas.

Boulder City, Nevada: Boulder City is a city in Clark County, Nevada.  It is approximately 26 mi southeast of Las Vegas.  As of the 2010 census, the population of Boulder City was 15,023.

Grand Canyon National Park Airport: Grand Canyon National Park Airport (IATA: GCN, ICAO: KGCN, FAA LID: GCN) is a state-owned public-use airport located in Tusayan, a CDP in unincorporated Coconino County, Arizona, United States.  It is near Grand Canyon National Park, seven miles (11 km) from the South Rim of the Grand Canyon.  The airport is primarily used for scenic tours and charter flights, but there is scheduled commercial service.

Westward Airways (United Kingdom): Westward Airways is an airline based at Land's End Airport, near St Just and Penzance in Cornwall, England, UK.  Until February 2009 it operated sight seeing flights in the local area, also running the former Lands End Flying School and is the operator of Land's End Airport.  After a review of the operations, it was decided to close the Lands End Flying School as of Saturday 31 January 2009, after which point Westward Airways also terminated the operation of sightseeing flights.  Whilst the two Cessna 152s will be disposed of, the remaining pair of Cessna 172s are to be transferred to Westward Airway's sister company; the Isles of Scilly Skybus, who will then resuming sightseeing flights under their own AOC.

China Airlines: China Airlines (CAL) () () is the flag carrier and largest airline of the Republic of China (Taiwan).  It is headquartered in Taoyuan International Airport and has 12,607 regular employees.  China Airlines operates over 1,400 flights weekly to 118 airports in 115 cities (including codeshare) across Asia, Europe, North America and Oceania.  The cargo division operates 91 pure freighter flights weekly.  The carrier was, in 2013, the 29th and 10th largest airline in the world in terms of passenger revenue per kilometer (RPK) and freight RPK, respectively.  China Airlines has three airline subsidiaries: Mandarin Airlines operates flights to domestic and low-demand regional destinations; China Airlines Cargo, a member of Skyteam Cargo, operates a fleet of freighter aircraft and manages its parent airline's cargo-hold capacity; Tigerair Taiwan is a low-cost carrier established by China Airlines and Singaporean airline group Tigerair Holdings and is wholly owned by China Airlines Group.

Grand Canyon Scenic Airlines: Grand Canyon Scenic Airlines is an American regional airline based in Paradise, Nevada, United States.  It operates sightseeing flights from Boulder City Airport in Boulder City, Nevada.  Scenic has been owned by Grand Canyon Airlines since 2008.

Scenic Airlines: Scenic Airlines is an American regional airline based in Paradise, Nevada, United States.  It operates sightseeing flights from Boulder City Airport in Boulder City, Nevada.  Scenic has been owned by Grand Canyon Airlines since 2008.

Grand Canyon Airlines: Grand Canyon Airlines is an 14 CFR Part 135 air carrier headquartered on the grounds of Boulder City Airport, Boulder City, NV.  Grand Canyon Airlines also has bases at Grand Canyon National Park Airport, AZ, and Page Airport, AZ.  It operates sightseeing tours and scheduled passenger service over and around the Grand Canyon.  Its headquarters and main operation center is Grand Canyon National Park Airport and Boulder City Airport, Nevada.

1956 Grand Canyon mid-air collision: The 1956 Grand Canyon mid-air collision occurred on Saturday, June 30, 1956, at 10:30 am Pacific Standard Time when a United Airlines Douglas DC-7 struck a Trans World Airlines Lockheed L-1049 Super Constellation over the Grand Canyon within the boundaries of Grand Canyon National Park, resulting in the crash of both airliners.  All 128 on board both flights perished.  It was the first commercial airline crash to result in more than 100 deaths, and led to sweeping changes in the control of flights in the United States.  The location of the crash has been designated a National Historic Landmark.

John Hance: John Hance (1840 – January 8, 1919) is thought to be the first non-Native American resident of the Grand Canyon, US.  He opened the first tourist trail in the canyon in the late nineteenth century.  He started giving tours of the canyon after his attempts at mining asbestos failed, largely due to the expense of removing the asbestos from the canyon.  "Captain" John Hance was said to be one of the Grand Canyon's most colorful characters, and it had been declared by one early visitor that "To see the canyon only and not to see Captain John Hance, is to miss half the show."  Hance delighted in telling canyon stories to visitors, favoring the whopper of a tale over mere facts.  With a straight face, Hance told travelers how he had dug the canyon himself, piling the excavated earth down near Flagstaff (a dirt pile now known as the San Francisco Peaks).  Despite such questionable claims, Hance left a lasting legacy at the Grand Canyon, dying in 1919, the year the Grand Canyon became a National Park.  Hance was the first person buried in what would become the Grand Canyon Pioneer Cemetery.

Supporting paragraphs: Grand Canyon Scenic Airlines Boulder City, Nevada
Answer: Clark County