In the 2014-15 season, Aittokallio suffered from injury and indifferent form, playing with the Monsters and the Fort Wayne Komets of the ECHL.
Despite being tendered a qualifying offer by the Avalanche, Aittokallio opted to return to Finland to further his development in signing a two-year contract with Liiga club, Oulun Kärpät on 2 July 2015 [REF].