Question: How far away from the North Pole has the Keystone Air Service provided air charter service? 

Context paragraphs:
Alert, Nunavut: Alert, in the Qikiqtaaluk Region, Nunavut, Canada, is the northernmost permanently inhabited place in the world, at latitude 82°30'05" north, 817 km from the North Pole.  The entire population of Baffin, Unorganized, the Statistics Canada name for Qikiqtaaluk, is located here.  As of the 2016 census the population was reported as 62, an increase of 1,140% over the 2011 census.  It takes its name from HMS "Alert", which wintered 10 km east of the present station, off what is now Cape Sheridan, in 1875–1876.

Keystone Air Service: Keystone Air Service Ltd. was an airline that served Manitoba, Canada, with charter services to anywhere in North America.  Keystone had been flying since 1985 and provided air charter service to as far north as Alert, Nunavut.

Air Charter Limited: Air Charter was an early post-World War II private, British independent airline formed in 1947.  The airline conducted regular trooping flights to Cyprus as well as worldwide passenger and freight charter flights from its bases at Southend Airport and Stansted.  Following Freddie Laker's acquisition of Air Charter in 1951, Aviation Traders and Aviation Traders (Engineering) became associated companies.  From 1955, it also operated scheduled coach-air/vehicle ferry services.  These initially linked London and Paris (via Southend and Calais).  In 1958, the process of transferring Air Charter's coach-air/vehicle ferry operation to sister company Channel Air Bridge began.  In 1959, Air Charter became part of the Airwork group.  In 1960, Airwork joined with Hunting-Clan to form British United Airways (BUA).

Canadian Airways: Canadian Airways Limited was a Canadian regional passenger and freight air service based in Winnipeg, Manitoba.  It traced its history back to the founding of its precursor, Western Canada Airways, by James Richardson in 1926, and was fully established in 1930 following WCA's acquisition of a number of smaller regional competitors.  At its peak, Canadian Airways had a total of 51 aircraft of various types that provided both regular scheduled service between settlements as well as charter service to bush locations.  Canadian Airways was absorbed into the fledgling Canadian Pacific Airlines in 1942, following Richardson's death three years earlier.

Channel Air Bridge: Channel Air Bridge was a private British independent airline specialising in cross-Channel vehicle-cum-passenger ferry services.  Freddie Laker started Channel Air Bridge as a sister airline of Air Charter on a provisional basis in 1954.  Operations commenced in 1955.  In 1958, Channel Air bridge took over Air Charter's vehicle ferry services.  In 1959, both Channel Air Bridge and its sister airline Air Charter became part of the Airwork group.  In 1960, Airwork joined with Hunting-Clan to form British United Airways (BUA).  In 1962, BUA reorganised its vehicle ferry operations by merging Channel Air Bridge with Silver City Airways.  This resulted in the creation of British United Air Ferries in 1963.

United States Army Air Service: The Air Service, United States Army (also known as the ""Air Service"", ""U.S. Air Service"" and after its legislative establishment in 1920, the ""U.S. Army Air Service"") was the military aviation service of the United States between 1918 and 1926 and a forerunner of the United States Air Force.  It was established as an independent but temporary branch of the U.S. War Department during World War I by two executive orders of President Woodrow Wilson: on May 24, 1918, replacing the Aviation Section, Signal Corps as the nation's air force; and March 19, 1919, establishing a military Director of Air Service to control all aviation activities.  Its life was extended for another year in July 1919, during which time Congress passed the legislation necessary to make it a permanent establishment.  The National Defense Act of 1920 assigned the Air Service the status of "combatant arm of the line" of the United States Army with a major general in command.

Air charter: Air charter is the business of renting an entire aircraft (i.e., chartering) as opposed to individual aircraft seats (i.e., purchasing a ticket through a traditional airline).  While the airlines specialize in selling transportation by the seat, air charter companies focus on individual private aircraft and itineraries, urgent or time-sensitive cargo, air ambulance service, and other forms of "ad hoc" air transportation.  Some air charters brokers have been given economic authority to sell seats on private jets with mixed success.  Some air charter companies offer a large variety of aircraft, such as helicopters and business jets.  Charter jet categories include turbo props, light jets, mid-size jets, super mid-size jets, heavy jets, long-range jets and VIP airliners.

First Army Air Service: The First Army Air Service was an Air Service, United States Army unit that fought on the Western Front during World War I as part of the Air Service, First United States Army.  The First Army Air Service was the largest and most diverse Air Service combat organization of the American Expeditionary Forces in France, and most American Air Service combat units were assigned to it when assigned to the front.

Flamingo Air: Flamingo Air is a small airline in the Bahamas.  Its base of operations is the Grand Bahama International Airport in Freeport.  It also has offices in Marsh Harbour Abaco Airport, in Bimini International Airport, and in the Lynden Pindling International Airport, Nassau.  It provides scheduled service to several islands, as well as Air Charter service to the Bahamas and south Florida.

Auguste George Airport: Auguste George Airport (IATA: NGD, ICAO: TUPA) is the northern most airport in the British Virgin Islands and is located on the island of Anegada.  The airport is named for Captain Auguste George.  There are only a handful of air charter companies who serve the island, and currently there is no scheduled air carrier service.  Island Birds Air Charter and Fly BVI Ltd www.flybvi.com offer direct on-demand air charter service from Beef Island (Tortola), Virgin Gorda, St. Thomas, San Juan, Antigua and St. Maarten to the aerodrome on Anegada.  The company is also the originator of the Anegada Day Trip, arriving daily at 09:45 and departing for Beef Island or Virgin Gorda at 5:30 pm.  The Original Anegada Day Trip includes round-trip airfare, taxi service from the Auguste George Airport to the beach at Loblolly Bay, and a lobster lunch at The Big Bamboo beach bar & restaurant.  This service is also provided by Island Birds Air Charter (www.islandbirds.com).

Supporting paragraphs: Keystone Air Service Alert, Nunavut
Answer: 817 km