A wide-ranging list of changes to Boeing’s ill-fated 737 Max planes has been put forward by US regulators.
The Federal Aviation Administration (FAA) document details actions it wants to be made before the planes can fly again commercially.
The 737 Max has been grounded since March 2019 following two fatal crashes which killed 346 people.
Boeing hopes to get the 737 Max back in the air early next year after the changes are made.
Proposed changes include updating flight control software, revising crew procedures and rerouting internal wiring.
In a related report also published on Monday, the FAA said that Boeing’s own recommendations had sufficiently addressed the problems that had contributed to the two fatal crashes.
Once the proposals become official, Boeing can then make the changes and ready the planes for flight.
The design updates will need to be made to all planes delivered to airlines along with those not yet ordered or built.
“We're continuing to make steady progress towards the safe return to service, working closely with the FAA and other global regulators.
"While we still have a lot of work in front of us, this is an important milestone in the certification process,” a Boeing spokesman told the BBC.
While the company hopes to get the 737 Max flying again commercially by early 2021, airlines may still face weak demand due to the coronavirus pandemic and travel restrictions.
There are also other hurdles to overcome, including the development of pilot training programmes, independent technical reviews and the results of simulator tests.
Boeing is expected to carry out 737 Max simulator pilot training at Gatwick Airport, where British Airways has a major presence.
BA’s parent company IAG signed a letter of intent to buy 200 of Boeing's 737 Max planes last year.
The FAA proposals have taken more than 18 months and include the work of more than 40 engineers, inspectors, pilots, and technical support staff.
“The effort represents more than 60,000 FAA hours of review,” the agency said.
The 737 Max crisis has battered trust in Boeing which faces a number of ongoing federal, criminal and civil investigations.
The FAA proposals can be reviewed by the public for 45 days before a final ruling is made.