Airbus suffered a double blow on Tuesday as airlines warned they faced further delays on delivery of the A380 superjumbo and a new hitch developed with the plane maker's cost-saving plans. Dubai's Emirates airline, the biggest A380 customer, and Abu Dhabi-based Etihad Airways, both said they had received warnings of delivery delays on the world's largest passenger airliner - which is already two years behind schedule. Airbus confirmed that chief executive Tom Enders had written to all A380 customers telling them production had reached a critical phase. It announced a "major review" of A380 production last week. Separately, in Toulouse, French labour unions claimed victory in their battle to stop Airbus from selling some factories - a plan that is part of a major restructuring and job-cutting exercise.