US aviation regulators on Monday spelled out new requirements for the Boeing 737 MAX before the grounded jet is permitted to fly again.

The Federal Aviation Administration will require a number of changes to “address the unsafe condition” of the aircraft, the agency said in a notice set for a 45-day public comment.

The jet has been grounded since March 2019 following two deadly crashes.

Some of the changes have been publicly discussed by Boeing, such as upgrades to an anti-stall system that has been seen as a factor in both crashes, and modification to a sensor system that had played a role in the accidents.