Airbus Group NV has agreed to drop an order for six A380 superjumbos by Japanese low-cost carrier Skymark Airlines Inc., sources saidn, in a blow to a program that's struggled to keep customers.

Skymark can't afford the aircraft, said the sources, who asked not to be identified because the discussions are private. Negotiations between the two sides continue about compensation, and options range from delaying delivery to outright cancellation, another source involved in the talks said.

Losing the Skymark order extends a drought for the A380, which has failed to attract a new airline customer in two years and came away with no new business in July at the Farnborough Air Show, typically a forum for deals. Airbus's most loyal buyer for the aircraft is Emirates, with 50 in service and a total of 140 on order, almost half the backlog.