The head of one of Boeing's (BA -3.41%) most important customers said he is worried that the aerospace giant is going to move on from the 737 MAX crisis as if nothing has happened, one of the sharpest public rebukes of Boeing by an airline executive since the plane was grounded two years ago.

Boeing's 737 MAX was pulled from service in March 2019 following a pair of fatal accidents, and the post-crash investigations revealed a lot of embarrassing details about a lax safety culture inside the company.

A Boeing 787 Dreamliner in flight.

Image source: Boeing.

Boeing replaced its CEO, revamped internal controls, and last fall won approval to get the 737 MAX airborne again, but the company is also dealing with delays to its 777X program and manufacturing flaws that have temporarily halted 787 Dreamliner deliveries.

In an interview with influential industry news source The Air Current, Tim Clark, head of Emirates, said culpability for what has gone wrong rests with Boeing's board, "and that's where the buck should stop." He said that future relationships between the company and airlines "will be conditioned by what they see [Boeing executives] are doing to sort out their internal problems."

Though few airline execs have criticized Boeing publicly, in part because airlines are eager not to cause passengers to distrust its planes, privately they have voiced considerable frustration about the company over the past year.

In the interview, Clark said he believes he needs to speak up because "otherwise, we're just going to move on out of the MAX era, as if nothing has happened."

Emirates, which is focused mostly on long-haul international flights out of its Dubai hub, is a bedrock customer for some of Boeing's larger, more international-distance planes. The company accounts for about one-third of the 777X order book, but with the plane delayed until 2023, it is said to be considering switching some of its orders to other models.