Federal prosecutors plan to criminally charge a former Boeing Co. pilot they suspect of misleading aviation regulators about safety issues blamed for two fatal crashes of the 737 MAX, according to people familiar with the matter.

Mark Forkner, who was Boeing’s 737 MAX chief technical pilot during the aircraft’s development, is likely to face prosecution in the coming weeks, these people said. In his former role, Mr. Forkner served as the plane maker’s lead contact with the Federal Aviation Administration for how airline pilots...

Federal prosecutors plan to criminally charge a former Boeing Co. pilot they suspect of misleading aviation regulators about safety issues blamed for two fatal crashes of the 737 MAX, according to people familiar with the matter.

Mark Forkner, who was Boeing’s 737 MAX chief technical pilot during the aircraft’s development, is likely to face prosecution in the coming weeks, these people said. In his former role, Mr. Forkner served as the plane maker’s lead contact with the Federal Aviation Administration for how airline pilots should be trained to fly the new jet.

It couldn’t be learned what formal charge or charges Mr. Forkner might face. Boeing admitted in a criminal settlement reached with prosecutors earlier this year that two of its employees—unnamed in that agreement—conspired to defraud the FAA about 737 MAX training issues in order to benefit themselves and the company.

A Justice Department spokesman declined to comment. Boeing declined to comment.

David Gerger, an attorney for Mr. Forkner, didn’t respond Thursday to requests for comment. Mr. Gerger has said Mr. Forkner, a pilot and Air Force veteran, wouldn’t endanger pilots or passengers. Mr. Forkner left Boeing in 2018 and went to work for Southwest Airlines Co. , where he worked until last year.

The Wall Street Journal previously reported, citing people familiar with the matter, that prosecutors were focused on two employees: Mr. Forkner and another former Boeing pilot, Patrik Gustavsson, who also dealt with the FAA. Mr. Forkner persuaded regulators to approve excluding details of a new flight-control system known as MCAS from the 737 MAX’s pilot manuals, according to a U.S. House investigation. An attorney for Mr. Gustavsson declined to comment.

Wreckage at the crash scene of Ethiopian Airlines Flight 302 near Bishoftu, Ethiopia, in March 2019, the second of two Boeing 737 MAX airplanes to crash within five months, together taking 346 lives.

Photo: Mulugeta Ayene/Associated Press

A prosecution of Mr. Forkner would be the first attempt to hold a Boeing employee accountable for conduct that preceded the two fatal 737 MAX crashes, which occurred in Indonesia and Ethiopia. Following the first crash, on Oct. 29, 2018, which killed 189 passengers and crew aboard a Lion Air jet, the FAA group that dealt with Messrs. Forkner and Gustavsson learned that MCAS may have played a role in the disaster. Another 737 MAX airliner crashed in Ethiopia on March 10, 2019, killing 157 people. Federal investigators began their probe in late 2018 after the first crash.

Reducing differences between the 737 MAX and older models would help Boeing’s airline customers avoid more costly simulator training when pilots began flying the new plane. That, in turn, would make the 737 MAX more attractive to airline customers that might buy it, according to the company’s criminal settlement agreement.

The automated MCAS system has been blamed for putting the two Boeing 737 MAX jets into fatal nosedives. Accident investigators also cited airline and crew missteps. The accidents prompted a nearly two-year global grounding of the fleet and created the most serious corporate crisis in Boeing’s history. The FAA approved the aircraft to fly again late last year.

The MCAS system was initially designed to activate during certain flight conditions that airline pilots wouldn’t normally encounter. During the aircraft’s development, Boeing engineers expanded the system’s authority and the conditions that would trigger it.

In chat messages released by congressional investigators, Mr. Forkner suggested that he hadn’t told regulators that Boeing engineers made the MCAS system more potent and that pilots would be more likely to encounter it during flight. Mr. Forkner suggested in the messages that he hadn’t known about changes to the flight-control system. “So I basically lied to the regulators (unknowingly),” he said in one 2016 message.

Mr. Gerger has said that Mr. Forkner’s chat messages referred to problems with a simulator, not the aircraft, and that his communications with the FAA were honest.

Even after learning about the change, Boeing’s employees and the company itself didn’t disclose how MCAS actually worked to FAA personnel responsible for approving what amount of pilot training was needed, according to the company’s settlement agreement with the Justice Department. The employees “intentionally withheld and concealed” the change from the FAA, according to the agreement.

The settlement Boeing struck with prosecutors included other messages in which the company’s employees expressed that they felt pressured to have the jet approved for lighter pilot training, which could be done in a matter of hours using a computer or tablet.

The settlement stated that the misconduct was “neither pervasive across the organization, nor undertaken by a large number of employees, nor facilitated by senior management.”

In its settlement with the Justice Department, filed in the Northern District of Texas, where some of Boeing’s airline customers are based, the company agreed to pay a nearly $244 million fine.

The deal said Boeing’s employees conspired to defraud the FAA from 2016 to 2018, a period during which air-safety regulators were deciding what training would be needed for airline pilots to fly the new jet. The agreement included almost $2.3 billion in compensation to airline customers and families of the 346 people who died in two MAX crashes.

Write to Dave Michaels at dave.michaels@wsj.com and Andrew Tangel at Andrew.Tangel@wsj.com