Using those latest figures, Danish bank Sydbank reported that SAS had 29.54 million passengers over the past 12 months.
Budget carrier Norwegian had 29.66 million passengers over that same period, marking the first time that Norwegian has topped its main rival.
Norwegian also came out on top last month, flying 2.1 million passengers to SAS's 1.9 million. Norwegian's figures represented a 20 percent increase over the same month last year while SAS saw 9.8 percent growth.
The new milestone for Norwegian comes after several years of aggressive expansion, with the company purchasing many new aircraft and opening new routes across Europe. In 2005, Norwegian had just 13 planes compared to the 99 it had a decade later.
According to the company's order books, more than 200 additional aircraft will join the fleet in the coming years.
Norwegian was established in 1993, while SAS's history dates back to 1946 when the state-owned airlines in Denmark, Norway and Sweden were merged. The three nations have since sold parts of their ownership and today Sweden owns 17 percent of the airline, while Denmark owns 14 percent and Norway 11 percent.