Aittokallio was first selected to represent Finland at the 2009 World U-17 Hockey Challenge tournament organised by Hockey Canada. With an understrength team, Aittokallio mirrored the Finnish team and went winless in three games for the tournament to finish tenth out of ten. Touted for his hockey intelligence, good reflexes and athleticism, Aittokallio was selected to be first choice goaltender for Finland at the 2010 World Under-18 Championships in Minsk, Belarus. Sami, however, missed the tournament after suffering an ankle injury as Finland went on to defend their Bronze medal against Russia.