But it is still not certain when the planes which were grounded worldwide this month,will be allowed to fly.
Investigators have not yet determined the cause of the accidents.
As part of the upgrade,Boeing will install an extra warning system on all 737max aircraft.which was previously an optional safety feature.
Neither of the planes operated by lion air in Indonesia and Ethiopian Airlines,that were involved in the fatal crashes carried the alert systems ,which are designed to warn pilots when sensors produce contradictory readings.
Boeing said that airlines would no longer be charged extra for that safety system to be installed.
The plane maker has issued an upgrade to the software that linked to the accident.
The manoeuvering characteristics augmentation system better known as MCA's,is software designed to help prevent the 737 max from stalling.
It reacts when sensors in the nose of the aircraft show the jet is climbing at too steep an angle,which can can cause a plane to stall.
But an investigation of the lion airflight last year suggested the system malfunctioned and forced the plane nose down more than 20 times before it crashed into the sea.
The Us Federal Aviation Administration (faa)says there are similarities between that crash and the Ethiopian accident on 10 march.
Therefore Boeing has redesigned, the software so that it will disable MCAS if it receives conflicting data from its sensors.
And lastly Boeing said a final version of the software would be submitted to the federal Aviation Authority (Faa) by the end of the week.