Europe and Canada said they would seek their own guarantees over the safety of Boeing's 737 Max, further complicating plans to get the aircraft flying worldwide after they were grounded in the wake of two accidents killing more than 300 people.

As the U.S. Federal Aviation Administration (FAA) analyzes Boeing's plans for a software fix prompted by the first crash five months ago, the European Union's aviation safety agency EASA promised its own deep look at any design improvements.

"We will not allow the aircraft to fly if we have not found acceptable answers to all our questions," EASA Executive Director Patrick Ky told an EU parliament committee hearing.