Ryanair's net profit more than doubled in its April-June quarter on higher-than-expected last-minute fares and the timing of the Easter holidays, while bookings for rest of the summer are "robust", Europe's largest low-cost carrier said on Monday.

Ryanair Holdings Plc said that any tariff cost would be on Boeing Co. to bear, as the Irish budget airline demanded a return to a no-duties regime that that has governed the industry for close to half a century.

Ryanair boss Michael O'Leary has said the airline is considering increasing a bonus it pays to workers for identifying passengers with oversized bags. Staff currently receive €1.50 (£1.30) if they intercept customers who are trying to bring bags that are too large on a Ryanair plane.