2008-09: Sami Aittokallio played for Ilves in the U-20 Junior "A" league. In 12 games, Aittokallio posted a 2.24 goals-against average and a .920 save percentage.
2009-10: Aittokallio played for Ilves in the U-20 Junior "A" league. In 23 games, Aittokallio registered a 3.20 goals-against average and a .899 save percentage. In 9 playoff games, he posted a 2.26 and a .925 save percentage. Ankle injury kept him off the U-18 World Championships team.
2010-11: Aittokallio appeared in 18 SM-Liiga games for Ilves Tampere as an 18-year-old and was the backup to Flames' prospect Joni Ortio for Finland's entry at the 2011 U20 World Junior Championship. In 16 regular season games for Ilves, Aittokallio was 5-8 with 1 shutout and had a 2.73 GAA and .909 save percentage. In two playoff games he was 0-2, allowing 5 goals on 56 shots and finishing with a 2.57 GAA. He saw one period of action for fifth-place Finland at the junior tournament and stopped all seven shots he faced. He also skated in six games for Leki in Mestis (Finland's second men's league) and nine games with Ilves' U20 team.
2011-12: Aittokallio appeared in 11 SM-Liiga games for Ilves and was a standout for Finland at the 2012 U20 World Junior Championship – seizing the starting role from Kings' prospect Christopher Gibson. Skating for last-place Ilves in SM-Liiga action, he was 1-6-3 with a 2.82 goals against and .910 save percentage. He did not play in the relegation series against Mestis champion Vaasa Sport. In seven games on loan to Leki in Mestis he was 1-6 with a 4.33 goals against and .871 save percentage. He played five games for Finland at the WJC and was 3-2 with 1 shutout. He stopped 38 shots in a win over the USA and made 55 saves in a shootout loss to Sweden in the semifinals. He finished the tournament with a 2.52 goals against and .936 save percentage. In six games with the Ilves U20 team he was 2-4 with a 3.11 goals against and .905 save percentage.
2012-13: Aittokallio made his NHL debut in April, getting the start against the defending Stanley Cup champion Los Angeles Kings, and backed up Calvin Pickard with Colorado's AHL affiliate Lake Erie in his first season in North America. He stopped 23 of 25 shots against the Kings before leaving the game in the third period due to leg cramps (The Kings eventually won the game 3-2 in a shootout). Aittokallio was 14-12-1 with 1 shutout in 27 AHL games and had a 3.00 goals against and .899 save percentage. Lake Erie finished third in the North Division but missed the AHL playoffs.
The Finnish netminder has been blessed with tremendous reflexes. Notably quick and athletic, Aittokallio needs to work on the technical side of his game to ensure more consistent performances.
Aittokallio is currently backing up Calvin Pickard for the Lake Erie Monsters but his play earned him a one game call up last season for the Avalanche. If he can get his technical game up to par, Aitokallio has the talent to be a number one goalie in the NHL.