Aas, who started for the Rustad IL , made her debut in Beitostølen in November 2000 in the cross-country skiing world cup , finishing 72nd over 10 km classic. In the following month she ran her first race in the Continental Cup in Orsa and achieved 41st place in the sprint. In the 2004/05 season she came in the Scandinavian Cup twice under the top ten and thus reached tenth place in the overall standings. In March 2005 she got her first World Cup points with 29th place in the sprint in Drammen . In the same month she was fourth in the Birkebeinerrennet . In the 2005/06 season she achieved fifth place overall in the Scandinavian Cup with five top ten finishes. In February 2006 she achieved fourth place over 15 km in Haanja, her best place in this racing series. She completed her 12th and last individual World Cup race in Drammen in March 2006, which she finished in 19th place in the sprint and thus achieved her best individual placement in the World Cup.
Norway