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