Difference in flight number

Hi, I was wondering why certain flight numbers are different.
The flight SK061 for example, is in your system SAS61. Do your service add the company name and the flight name together?
I’m getting SK061 from Arlanda (Stockholm) and SAS61 from you and I’m just wondering which is right and why they differ.

SAS and SK are both valid airline codes for Scandinavian Airlines Systems.

We normalize all flight idents to use the ICAO airline identifiers (3 characters), since that is the designator that is actually used by pilots and air traffic control for representing the flight. By historical convention, airlines and travel agencies use the older IATA airline identifiers (2 characters), but due to the size limitation there are known conflicts and duplicated IATA codes throughout the world. Using ICAO identifiers avoids ambiguity by preventing such conflicted assignments. Our website generally shows both identifiers simultaneously to avoid such user accessibility issues.