Donald Trump has tapped a former Delta executive to lead the Federal Aviation Administration as the regulator deals with questions about its approval of a Boeing airliner involved in two deadly crashes within five months.

The White House said Tuesday that Trump will nominate Stephen Dickson to head the FAA. The agency has been led by an acting administrator since January 2018.

Separately, the transportation department confirmed that its watchdog agency will examine how the FAA certified the Boeing 737 Max 8 aircraft, the now-grounded plane involved in two fatal accidents within five months.

The FAA had stood by the safety of the plane up until last Wednesday, despite other countries grounding it.

The transportation secretary, Elaine Chao, formally requested the audit in a letter sent to the department’s inspector general, Calvin Scovel III, on Tuesday.

Chao, whose agency oversees the FAA, said the audit would improve the department’s decision-making. Her letter confirmed that she had previously requested an audit. It did not mention reports that the inspector general and federal prosecutors are looking into the development and regulatory approval of the jet.

The letter requests “an audit to compile an objective and detailed factual history of the activities that resulted in the certification of the Boeing 737 Max-8 aircraft”. It also says the audit will help the FAA “in ensuring that its safety procedures are implemented effectively”.

Boeing said in a statement Tuesday that it would fully cooperate with the audit.

Questions about the FAA’s handling of the issue extend beyond US borders and will pose an immediate challenge for Dickson, if he is confirmed to lead the agency.

The Canadian transport minister, Marc Garneau, said this week that even if the FAA certified Boeing’s fix for the software on the 737 Max jet, “we will do our own certification”.

Dickson was Delta’s senior vice-president of flight operations until retiring on 1 October, after 27 years with the airline, including time flying the 737 and other Boeing jets. Before that, he was an air force pilot. He emerged in recent weeks as the likely choice to lead FAA.

For the past 14 months, the agency has been under an acting administrator, Daniel Elwell, a former air force and American Airlines pilot.

A Lion Air Boeing 737 Max 8 crashed off the coast of Indonesia last October, and an Ethiopian Airlines Max 8 crashed this month near Addis Ababa.

Investigators suspect that incorrect sensor readings feeding into a new automated flight-control system may have played a role in the Indonesian crash, and the Ethiopian plane had a similar, erratic flight path.

Boeing began working on an upgrade to software behind the flight-control system shortly after the Lion Air crash. Boeing’s CEO, Dennis Muilenburg, said in recent days that the company was close to finishing the update and changes in pilot training to help crews respond to faulty sensor readings.

Elwell told House transportation committee members that Boeing expected the software update to be finished by Monday, according to a person familiar with the briefing who spoke on condition of anonymity because they are not authorized to speak on the timing publicly. The FAA earlier required design changes to the flight-control system “no later than April”.

After Boeing finishes the software, the FAA still must approve it.

The Associated Press reported on Monday that the justice department was investigating development of the Max, according to a person briefed on the matter. It is unclear when those inquiries began.

The justice department and the transportation department’s inspector general are examining the way Boeing was regulated by the FAA, according to a person familiar with the matter and who asked not to be identified because the inquiry is not public.

Critics have questioned the FAA’s practice of using employees of aircraft manufacturers to handle some safety inspections. FAA inspectors review the work of the manufacturers’ employees, who are on the company payroll and could face a conflict of interest.

A federal grand jury in Washington sent a subpoena to someone involved in the plane’s development seeking emails, messages and other communications, the person told the Associated Press.

A report in the Wall Street Journal on Sunday said the inspector general was looking into the plane’s anti-stall system. It quoted unidentified people familiar with both cases.

The 29 October Lion Air crash killed 189 people, and 157 died in the 10 March accident involving an Ethiopian Airlines jet. Both accidents happened shortly after takeoff.

Other countries banned the Max 8 and a slightly larger model, the Max 9, in the days after the Ethiopian crash. The FAA and US airlines that use the planes stood by the plane’s safety until last week.

There are about 370 Max jets of various models at airlines around the world. American, Southwest and United have said the grounding of their Max jets has led to some canceled flights.

The plane is an important part of the Chicago-based Boeing’s future. The company has taken more than 5,000 orders and delivered more than 250 Max jets last year. Boeing still makes an older version of the popular 737, but it expected the Max to account for 90% of all 737 deliveries this year.

