Four Chinese airlines will buy a total of 292 planes from Airbus in a $37 billion windfall for the aviation giant, the carriers said in separate statements Friday. China Eastern said it had agreed to purchase 100 A320neo jets and China Southern said on the same day that it would buy 96 of the same model. Air China and its subsidiary Shenzhen Airlines also confirmed the purchase of a combined 96 A320neo planes, according to separate filings.