The Ryanair business model was never, ever going to be sustainable, as I've said on numerous occasions.
For the record, that model is:
1. Sell product below cost of production.
2. Drive competitors out of business.
3. Profit!
It worked just fine for Stagecoach. As long as you've got plenty cash in the bank, which isn't one of Ryanair's problems, it's perfectly valid. Just not nice