The president of Emirates, an airline based in Dubai, Tim Clark said that unless Rolls-Royce and GE (General Electric) fix their reliability and are truly ready, the airline wouldn't take any new Boeing or Airbus planes.

The airline has an order of 150 777Xs. In 2017, it also ordered 40 787s.

However, according to Clark, Emirates said it could replace some 777Xs with 787s.

Though he still wants the 777X, he doesn't like the delay and the uncertainty of a time frame for delivery.

He said that with regards to the 787, he wouldn't commit to it due to instability in the Rolls-Royce engine program.

Rolls-Royce makes the 787 airplane's engine.

His concerns over Rolls-Royce came up when it wasn't able to make engines under his specifications and this affected his decision on not willing to complete a contract for Airbus A330neos and A350s.

He said that airlines should be given "engines that work from day one" and it that isn't possible, then manufacturers better not make them at all.

He also added because he had been in this business for a long time, he had seen airline and engine developments with problems.

However, these days, airlines are asked to deal with those problems by working with manufacturers.

He said that once the inability to give the Emirates airplanes and engines that work comes up, then, it's over.

Clark also stressed the foolishness of making new contracts until he's sure that the "aircraft will do what they said they were going to do."

Boeing delayed the release of the ultra-long-range version of its 777X widebody because of, among other things, issues with its GE engines.

Because of what's happening, Clark said it is not unreasonable to re-evaluate jet orders that were made 2-3 years ago but noted that engine issues are not a good excuse to re-think backlog of aircraft orders.

Clark clarified that Emirates wants 99.5 percent reliability from its airplanes and expects little maintenance during the first five years of any of their aircraft.

He went on further to say that the A330, 787 - 9 and -10 including the A350 are "hugely potent aircraft" that will have "their operations sorted out" but they're not being made the way they should be.

Emirates will abide by its purchase contract but he said contracts state that airlines can decline an aircraft that do not meet its specifications for fuel burn, range, and other metrics.

A Boeing spokesman reiterated that their priority is the safety and performance of their aircraft and they are working with GE and Rolls-Royce because they can resolve some challenges with the engines.