Boeing has reported its largest-ever quarterly loss, with the manufacturer losing $3.4 billion (£2.7 billion) over the past three months.

The financial damage comes as the entire fleet of flagship 737 Max planes remains grounded.

The planes were banned from the skies in March this year after issues with the model were linked to an Ethiopian Airlines flight crash that killed 157 people.

Five months earlier, 189 people were killed when a Boeing 737 Max operated by Lion Air crashed.

Boeing reported second-quarter revenue of $15.8 billion.

“This is a defining moment for Boeing, and we remain focused on our enduring values of safety, quality, and integrity in all that we do, as we work to safely return the 737 MAX to service,” said Boeing chairman, Dennis Muilenburg.

“During these challenging times, teams across our enterprise continue to perform at a high level while delivering on commitments and capturing new opportunities driven by strong, long-term fundamentals.”

Boeing said it was working “very closely” with the FAA on a process to certify a 737 Max software update and safely return the plane to service.

While testing is underway, no date for the return was announced.

Muilenburg warned an extended delay might forced Boeing to cease production.

“Should our estimate of the anticipated return to service change, we might need to consider possible further rate reductions or other options, including a temporary shutdown of the Max production,” he told analysts in a conference call.

After the two crashes, production of the 737 Max was reduced from 52 to 42 aircraft per month.

Having to suspend deliveries of new planes has hit cash flow and profit margins at Boeing.