The U.S. aviation regulator will significantly change its oversight approach to air safety by July following two fatal Boeing Co Max 737 passenger plane crashes, according to written congressional testimony seen by Reuters.

At a U.S. Senate panel hearing on Wednesday, the Federal Aviation Administration (FAA) acting head Dan Elwell will say the agency's oversight approach must "evolve" after the deadly crashes, according to the testimony.

The aviation industry has been thrown into flux by a Lion Air crash in Indonesia last October that killed 189 people and an Ethiopian Airlines disaster on March 10 that killed 157, both involving Boeing's 737 Max single-aisle plane.