But it definitely is a perfectly reasonable abbreviation!
No it bloody isn't. Anyone with an informed opinion would know that OS is Austrian Airlines. Stop being sloppy and lazy. Google "Open Skies IATA code" and less of the crap I see a lot of below.
AL = Air Lingus
BM = British Midland
FGS = Flyglobespan
I'll have a consonant please Carol......
10/10 if you spot the deliberate error on my part