' Boeing 737 MAX won't be recertified until 2020'

Boeing's 737 MAX aircraft, which has been grounded since March following two deadly crashes, will not be cleared to fly until 2020, the top US regulator said Wednesday.

Federal Aviation Administration chief Steve Dickson told CNBC the process for approving the MAX's return to the skies still has 10 or 11 milestones left to complete, including a certification flight and a public comment period.

"If you just do the math, it's going to extend into 2020," Dickson said.

Boeing has been aiming to win regulatory approval this month, with flights projected to resume in January.

But Dickson said, "I've made it very clear Boeing's plan is not the FAA's plan." He added that "we're going to keep our heads down and support the team in getting this report done right."

Boeing and the FAA have been under intense scrutiny following crashes that together killed 346 people and have prompted Boeing to cut production of the top-selling jet while new plane deliveries are suspended.

Dickson was expected to face another round of tough questioning at a congressional hearing later Wednesday.

Lawmakers have questioned whether the crashes were the result of FAA officials being too cozy with Boeing, leading to lax oversight during the original certification process for the aircraft.