Capacity (seats/planes/routes) will grow 20% or greater for the next 5 years, as no airline will beat Ryan on price, and there's plenty of available opportunity for growth within Europe. Earnings will actually grow faster than capacity, since ancilliary revenues are higher margin than seat sales.
Ryan is solidly profitable, and grows like an internet company, so at some point in the future this will be recognized by the market, and it will get the 25-35 multiple it deserves. But multiple expansion is not needed for the 3 year double in share price.
I like the company near term, medium term, and long term; currently it's my favorite idea.