A top aviation regulator in Europe said Boeing’s grounded fleet of 737 MAX planes would be allowed to fly again before the end of 2020 after making necessary changes.

According to Bloomberg.com , European Union Aviation Safety Agency (EASA) executive director Patrick Ky said several test flights conducted in September satisfied regulators about the safety of the aircraft.

EASA is now performing final document reviews and will develop an airworthiness directive scheduled to be issued in November. After another four weeks of public comment, the plane should be ready to take to the European skies again.

EASA did mandate that Boeing must develop “a so-called synthetic sensor to add redundancy,” which the manufacturer said would take between 20 and 24 months. The sensor will be required on the larger Max 10 variant scheduled to debut in 2022 and retrofitted on other MAX planes.

“Our analysis is showing that this is safe, and the level of safety reached is high enough for us,” Ky told Bloomberg. “What we discussed with Boeing is the fact that with the third sensor, we could reach even higher safety levels.”

While EASA is working on getting the MAX fleet approved by the end of 2020, the Federal Aviation Administration (FAA) has refused to reveal a timetable for when the grounded planes would be authorized to fly again.

Last month, FAA chief Steve Dickson and his top deputy Daniel Elwell conducted a test flight of the updated 737 after completing the training course that Boeing and regulators have proposed for all MAX pilots.