Cathay Pacific Airways says that it is "satisfied" with the Boeing 747-8 freighters and remains on track to take delivery of its first aircraft in October.
Cargolux, the launch customer for the 747-8F, rejected the first two aircraft that had been due for delivery on 19 and 21 September, citing "unresolved contractual issues" with Boeing.
"Cathay Pacific's commercial arrangements with all its suppliers, including Boeing, are confidential. However, we are satisfied that our commercial arrangements with Boeing take account of the known and disclosed specification and performance characteristics of the aircraft," said Hong Kong's flag carrier in a statement.
The airline added that it is on track to receive the first of 10 747-8Fs that it has ordered.
"The news mentioned will not affect Cathay Pacific's own deliveries. We expect to take delivery of our first 747-8F in October this year," said the Oneworld alliance member.
Negotiations between Boeing, engine supplier GE Aviation, Cargolux and 35% stakeholder Qatar Airways centre on the freighter's performance targets.
However, sources say that the issue also appears to be the compensation to Qatar from Boeing for the delays to its Boeing 787s.
Boeing has acknowledged the gap in the 747's performance, saying that the first aircraft would be "somewhat short of initial specifications for fuel burn". However, these are believed to have been known to customers for more than a year.
Cargolux, which has 13 747-8Fs on order, said that it has put on hold the financing for the freighters and is prepared to seek alternatives should the negotiations fail.
"In the event that the issues cannot be resolved in a timely manner, Cargolux will source alternative capacity to fully meet customer demand and expectations ahead of the traditional high season," said the airline.
Cargolux has assembled a new board of directors following the recently completed acquisition by Qatar Airways of a 35% shareholding in the Luxembourg-based freight specialist.
Siva Govindasamy contributed to this story.