There are no scheduled direct or even semi direct connections currently that I know of. In the past there have been seasonal flights between Whitehorse and Fairbanks with a canadian airline, but I don't believe any of those are still operating. Air North did and may still do cruise ship charters from Dawson - Fairbanks in the summers, so that may be how your friends managed.
Fairbanks to Dawson is most commonly done via Top of the World hwy. It's a days drive, and some sections of semi rough roads when you get north of Chicken. That's the easiest.
When we have to fly that way, it's usually via Vancouver. It's pretty terrible, and depending on the time of year involves a lot of stops along the way. Which is why driving is the way to go.