I used an airline travel hack to turn a layover into a mini-vacation and save on airfare. Sergei Gapon/Anadolu Agency via Getty Images, Gentry Hale

After five fabulous days exploring Norway's stunning fjords in mid-September, I was excited to try an airline travel hack I'd been eyeing for months: Icelandair's "stopover" program .

Icelandair allows passengers traveling between North America and Europe to stop in Iceland for up to 7 nights on a standard ticket without paying additional airfare . Higher-priced flex tickets allow up to 21 nights.

I chose a $455 one-way standard economy flight from Norway to the US with a four-day stop. All of Icelandair's transatlantic routes already pass through Keflavík International Airport near Reykjavík, making it an easy detour.

This strategy effectively added a second vacation onto my trip.…