United Parcel Service (UPS) has signed a new agreement with Airbus that changes the delivery dates for the ten A380 aircraft it has ordered.
The new agreement allows UPS to cancel its order if there are any more delays.
A withdrawal by UPS could be the last straw for the freight version of the superjumbo after the only other customer, FedEx, pulled out last year.
UPS expected its planes between 2009 and 2012 but was told the first one would be at least eight months late.
Airbus has now given UPS new estimates of when the aircraft will be ready, but the two have agreed not to make them public.
They are expected to decide later this year whether to go ahead with the order, which is valued at $2.8bn (£1.4bn).
Spread the pain
Electrical wiring problems have plagued the A380, which is about two years behind schedule.
Airbus says the first delivery will be made in October this year.
German Chancellor Angela Merkel and French President Jacques Chirac agreed earlier this Friday that they should divide equally the pain of job cuts and restructuring at Airbus.
EADS, which is the parent company of Airbus, is in the middle of a restructuring programme sparked by the delays to the flagship A380 programme.