Emirates is insisting on receiving its Airbus A350-1000s according to the original specifications and is voicing frustration with Airbus’ approach to customers with regards to the design changes announced at the Paris air show, Emirates Airline President Tim Clark told Aviation Week at the Dubai air show.

“We will not sanction an interruption of our growth program,” Clark says. “We have made that absolutely clear to Airbus. We have been held back too many times and have always regretted that we slowed down.”

Emirates has ordered 50 A350-900s and 20 A350-1000s which were originally planned to arrive in 2013 and 2015 respectively. Airbus has meanwhile shifted entry into service of the -1000 to 2017 and the -900 will not come before the first half of 2014. The airline placed an order for 50 additional Boeing 777-300ERs on the opening day of the Dubai air show.

The aircraft were originally planned to be used to fill the troughs between Emirates’ three banks at Dubai International Airport. The airline has been studying whether customers would be willing to accept transfer times of 5-6 hours and research concluded that there was a market for such connections. A significant amount of 777-300ERs were allocated to off-peak flying, but may now shift to strengthen the banks with the A350s being late.

Clark says “I cannot remember that we wanted new A350-1000 specifications and I wonder why they did not ask us before making the decision.” In his view, Airbus “kind of assumed that we would take it.” But Clark highlights increased maintenance costs, higher weights and overall a more expensive aircraft as his major concerns.

Airbus announced in Paris that the -1000 will be around 18 months late, mainly because of engine upgrades. But Clark is also skeptical about Rolls-Royce’s design changes. “If you ask me, the aircraft would have needed 105,000 pounds of thrust,” Clark says. “But that would have meant a bigger fan.

Clark is particularly worried about the delays because it keeps Emirates from standardizing its fleet at a high product level. The airline has been forced to keep its A330-200s and A340-300s much longer than has been planned. “That’s the only reason why we don’t get that five star rating that the other guys have. I’m sick of it,” Clark says.

Emirates has been in talks with Boeing on the next generation 777 and has been a vocal supporter of the project. Clark says he would be happy if the aircraft would reach 12-13% in efficiency gains over the current 777-300ER. He no longer expects Boeing to deliver the aircraft in 2017. Boeing has indicated the aircraft won’t be ready before 2018 or 2019.