I noticed this question was tagged fr (IATA code for Ryanair), and assumed that was an agreed-upon practice (like tagging airport-specific questions with IATA 3-letter airport codes). I went ahead and tagged this one with wn only to notice afterwards that it had already been tagged southwest-airlines, which got me wondering what kind of tags should we use...
Please review previous discussion on this theme:
fr is not valid and needs to be edited, as all short tags for airlines.
The problem with this short tags is that they are very ambiguous. fr could be as well be the top level domain for France.
So I would propose to use the full name.