Boeing Co.'s 737 Max certification, needed to end the jet’s nine-month worldwide grounding by regulators, will extend into 2020, the top U.S. aviation regulator said Wednesday.

Federal Aviation Administration chief Stephen Dickson said that the plane, which has been grounded worldwide since March, will not be certified to fly this year, dashing Boeing’s hopes of getting the popular family of planes back in the air in 2019.

“If you do the math, it’s going to extend into 2020,” Dickson told CNBC Wednesday before he is expected to testify before a congressional panel. “We’re going to do it diligently because safety is absolutely our priority with this airplane.”

Boeing erased gains in pre-market trading on Dickson’s remarks, falling 0.8 per cent to US$345 at 8:32 a.m. in New York.

Boeing said Nov. 11 that it hoped the FAA would approve its redesign of the 737 Max by the end of this year and write new training standards for the plane in January. It will still take airlines weeks or even months longer to get their planes back in the air.

Dickson’s comments come hours before he is scheduled to testify before the House Transportation and Infrastructure Committee. It will be the panel’s fifth hearing on the 737 Max and is likely to draw attention to missteps by the agency in its initial certification of the 737 Max.

The committee, which grilled Boeing President Dennis Muilenburg on Oct. 30, is turning its attention to how the FAA certified the plane with a flight control system implicated in two fatal crashes that killed 346 people.

--With assistance from Alan Levin.