The US Federal Aviation Administration issued an order on Wednesday to allow Boeing’s 737 Max to return to the skies, clearing the way for other regulators to follow and airlines to restore the plane to their schedules.

The move by US regulators, which had been expected, marks the beginning of the end of the worst crisis in Boeing’s century-long history. Two 737 Max crashes killed 346 people, and afterwards destroyed billions in Boeing’s market value, led to the departure of former chief executive Dennis Muilenburg and tarnished the reputation of one of the most storied US manufacturers.

The FAA is requiring that Boeing change flight control software, known as the Maneuvering Characteristics Augmentation System, or MCAS, which was a critical factor in the two fatal crashes which happened within five months. The software will be unable to activate repeatedly and can only do so with input from two sensors, instead of just one. The agency is also requiring changes to the plane’s wiring.