Irish carrier Aer Lingus, one of the first members of the alliance oneworld, has announced its desire to pull out of the group, which is headed by British Airways and American Airlines. "Alliance membership has inevitably become less relevant for the airline over time, with an increasing number of customers availing of our new direct services at low fares," Aer Lingus Chief Executive Dermot Mannion said.Why is Aer Lingus leaving? There are a few...