An official at Europe’s top aviation regulator said he is impressed with changes made to Boeing’s much-maligned fleet of 737 MAX airplanes and believes the plane is safe enough to be flown above European skies before the end of the year.

Patrick Ky, executive director of the European Union Aviation Safety Agency, said the jet passed a series of test flights in September, and the agency was preparing final documents that would clear the way for the fleet to be used.