A plane approaches the runway for take off.

Washington: Boeing and US aviation regulators are coming under intense scrutiny over the certification of the 737 MAX aircraft after news that two recent crashes of share similarities.

On March 11, just a day after the Ethiopia crash left 157 dead, a grand jury in Washington issued a subpoena to at least one person involved in the plane's certification, according to a Wall Street Journal article citing people close to the matter.

The subpoena, which came from a prosecutor in the Justice Department's criminal division, seeks documents and correspondence related to the plane, according to the report.

A criminal inquiry is "an entirely new twist," said Scott Hamilton, managing director of the Leeham Company, who recalled a probe of a 1996 ValuJet crash as the only other aviation probe that was not a civil investigation.

"Unlike France, where criminal investigations into aviation accidents seems common, it is very, very rare in the US," Hamilton added.

The Transportation Department's inspector general also is probing the approval of the 737 MAX by the Federal Aviation Administration (FAA), The Wall Street Journal also reported. Neither department responded to requests for comment from AFP.

The probe is focusing on the Maneuvering Characteristics Augmentation System, or MCAS, implicated in the Lion Air crash, which authorities have said shared similarities with the latest accident.

The Ethiopian Airlines crash on March 10 came less than five months after a 737 MAX 8 operated by Lion Air crashed in Indonesia, killing 189.