The head of Boeing has described the fatal crashes of two of its aircraft as a "defining moment" for the company.

Speaking to CBS television, Dennis Muilenburg said sorry to the families of the 346 people killed in separate disasters within months of each other in Ethiopia and Indonesia.

"I do personally apologise to the families... we feel terrible about these accidents," he said.

In April, a few weeks after the Ethiopia Airlines crash, Mr Muilenburg had said sorry on behalf of the company.

That apology was "too little, too late" for the pilot's father, Getachew Tessema.

Both the Ethiopian and Indonesian crashes involved the 737 Max model, Boeing's most lucrative aircraft. 

Its anti-stall system has been identified as the common factor in both crashes. All the planes have been grounded since the Ethiopia Airlines disaster in March and are unlikely to fly again before August. 

In the interview, Mr Muilenberg reiterated his company's commitment to safety.