Ryanair shares have been given a "buy" rating by US investment bank CS First Boston. Ryanair's strategy was "one of the best defined in the airline industry", according to the investment bank which has just started coverage of the stock. The shares offered "an opportunity for profit growth in a company that is well-positioned to take advantage of Europe's deregulating airline envirnoment", the bank said. Ryanair shares gained 15p this week to close yesterday at 400p.