To make sure its frequent flyers stayed with it for long-haul trips, Alaska struck code-share deals with 15 airlines to tap into their global networks.

WSJ: The Weekend Interview with Bill Ayer: An Airline That Makes Money. Really.

Singapore Airlines has increased its stake in Virgin Australia to tap into the Australian market and counter the strength of its rivals.

BBC: Singapore Airlines increases stake in Virgin Australia

Panama's Copa Airlines, United Arab Emirates' Etihad Airways and TAP Portugal.

WSJ: El Al, Virgin Atlantic Are Airlines That Auction Upgrades to Business Class