Oslo can be reached from all continents and most capitals in Europe with direct flights.
Oslo Airport Gardermoen is one of the most modern airports in Europe and is situated 50 km from the city centre of Oslo. The Airport Express Train Flytoget takes you from the airport to Oslo Central Station in 19 minutes. Trains depart every 10 minutes. The fare is 210 NOK (approx. 21 Euro) one way. You can buy tickets as you embark the train (just swipe your credit card at the gate), online at www.flytoget.no/en/ or on the Flytoget app.
You may also reach Oslo by flying to Sandefjord Lufthavn Torp. From here, you can take a direct bus to reach Oslo in 1 hour and a half or a train from Torp Station with a similar journey time.