If you come from europe, fly with www.airgreenland.com from Copenhagen to Kangerlussuaq. The trip goes via Nuuk where you change planes, from there either direct to Kangerlussuaq or with a short stop in Sisimiut on the way.
If you come from North America, it is possible to fly over Iceland, Keflavik-Nuuk-Kangerlussuaq. New airport opens in Nuuk at the end of 2024, and flight routes and options are therefore not yet known.