Oulu Airport — Oulu / Oulunsalo, Finland

As the busiest airport in Finland after Helsinki, OUL underscores how much economic weight the northern city of Oulu carries despite sitting just below the Arctic Circle on the Gulf of Bothnia. The region built its modern reputation on technology, anchored historically by Nokia's research presence and now sustained by a broader cluster of telecommunications and software firms that keep business travel demand high year-round. Finnair operates frequent shuttle-like service between Oulu and Helsinki, a route that functions almost like a domestic commuter link given how central it is to companies headquartered in the capital with operations up north. Winter conditions, including extended darkness and heavy snow, shape much of the airport's operational rhythm, and its runway and de-icing infrastructure are built to handle a climate considerably harsher than that of most European airports of comparable size and traffic.