A US federal grand jury on Thursday charged a former Boeing chief test pilot with misleading aviation regulators during the certification process for the 737 MAX, which was involved in two fatal crashes.

Mark Forkner, 49, was the lead contact between the aviation giant and the Federal Aviation Administration (FAA) over how pilots should be trained to fly the planes.

Forkner "provided the agency with materially false, inaccurate, and incomplete information about a new part of the flight controls for the Boeing 737 MAX" flight handling system, called the Maneuvering Characteristics Augmentation System (MCAS), the Justice Department said in a statement.

The MCAS, which is blamed for the crashes in 2018 and 2019, was supposed to prevent the plane from going into a dive, but instead malfunctioned.

According to court documents, Forkner had discovered information in 2016 about a major change made to the MCAS that was supposed to prevent stalling, but deliberately chose not to share the details with the FAA.

As a result, the FAA did not include a reference to the MCAS in training manuals for pilots.

Boeing has acknowledged its responsibility in misleading regulators and agreed to pay more than $2.5 billion dollars to settle lawsuits. The aviation giant has also admitted that two of its employees misled the FAA.

Forkner is the first individual to be prosecuted in this case.

In a message to a colleague revealed in 2019, Forkner said that the MCAS made the aircraft difficult to fly in a simulator.

But he deliberately chose not to share that information with the FAA, which led to the regulator not requiring specific pilot training for or including any reference to the MCAS in training materials.

Forkner bragged to his colleague that he had lied to the regulator. According to documents published in early 2020, he also boasted that he could deceive his FAA contacts to obtain certification for the MCAS.

A former Boeing chief test pilot provided the Federal Aviation Administration with "materially false, inaccurate, and incomplete information" about the 737 MAX flight handling system, according to the US Justice Department
A former Boeing chief test pilot provided the Federal Aviation Administration with "materially false, inaccurate, and incomplete information" about the 737 MAX flight handling system, according to the US Justice Department AFP / Jason Redmond

Forkner is also accused of conspiring against Boeing customers who purchased 737 MAX aircraft by withholding critical information.

The 737 MAX was formally certified in March 2017 and made its first commercial flight a few weeks later.

But in October 2018, a Lion Air plane crashed into the sea shortly after takeoff, killing all 189 people on board.

In March 2019, an Ethiopian Airlines 737 MAX crashed, killing 157 people.

In both cases, the MCAS had run amok based on faulty information transmitted by one of the aircraft's two sensors.

It wasn't until October 2018, after the first crash, that the FAA learned key details about the MCAS.

All 737 MAX planes were then grounded worldwide for 20 months. The MAX was allowed to fly again at the end of 2020, once the MCAS software was modified.

Forkner was formally indicted Thursday by a grand jury in Texas on two counts of fraud involving aircraft parts and four counts of wire fraud.

If convicted, he could face up to 100 years in prison.

"Forkner allegedly withheld critical information from regulators," said Texas federal prosecutor Chad Meacham.

"The Department of Justice will not tolerate fraud -- especially in industries where the stakes are so high."

When contacted by AFP, Boeing declined to comment.