The Finnish Air Force Museum, at Tikkakoski north of Jyväskylä, is the country's main museum for military aviation. Its hangars hold aircraft, engines, weapons, uniforms, models, and archive material tracing Finnish flying from the early 20th century through the Second World War and Cold War. Aviation enthusiasts will find far more here than a casual display.
The museum is outside the city centre, so it is easiest with a car or a planned bus connection. It is worth the effort if you are interested in Finland's wartime history, small-country defence, or aircraft design. Non-specialists may prefer Jyväskylä's architecture and lakefront first, but this is a strong second-tier sight.