Boeing has admitted it made a “mistake” in handling a gltich that led to two fatal crashes, killing over 300 people.

Boeing CEO Dennis Muilenburg says the company’s communication with regulators and the public “was not consistent and that's unacceptable”.

The US Federal Aviation Administration has slammed Boeing for not telling regulators that a safety indicator in the cockpit of the 737 MAX jets did not work as intended.

It is unclear whether either of the crashes could have been prevented if the cockpit alert had functioned properly.

“We clearly had a mistake in the implementation of the alert,” Mr Muilenburg said.

The 737 model in question remains grounded worldwide while regulators approve Boeing's long-awaited fix to the software.

Mr Muilenburg described the Lion Air and Ethiopian Airlines crashes as a “defining moment” for Boeing.

Recently released audio between Boeing and pilots shows them discussing the automated flight-control system just months before the second fatal crash.