Alykel International Airport — Norilsk, Russia

Norilsk ranks among the largest permanently inhabited settlements built above the Arctic Circle, a mining city whose nickel and palladium smelters have made it one of the most polluted industrial centers in Russia, and Alykel Airport, carrying the code NSK, functions as the settlement's essential lifeline rather than merely a convenience. No roads or railways connect Norilsk to Russia's wider transport network; residents and cargo depend on flights from this airport or river and rail links to the port of Dudinka, making NSK one of the few airports anywhere that a city's population genuinely cannot do without. Winters bring weeks of continuous polar night alongside extreme cold, conditions that demand specialized de-icing and runway maintenance well beyond what most commercial airports require. Nornickel, the mining conglomerate that dominates the local economy, relies on the airport to rotate workers and equipment in and out of a region otherwise cut off for much of the year.