Several airlines are offering direct international flights from European airports to Tromsø. So you do not have to make a stop over in Oslo. It is not just saving you time, also by early booking the price is much more attractive. Depending on the season you can book your ticket for example with Lufthansa from Frankfurt - Tromsø or from Zürich to Tromsø with Helvetic Airways. Also Air Norwegian is offering several times a week a connection from and to London Gatwick, as SAS is flying also from Tromsø to Stockholm. So you will have more time to chase the Northern Lights in a camper or for another fishing trip.