A Boeing 737 MAX 8 airliner takes off from Renton Municipal Airport near the company's factory, on March 22, 2019 in Renton, Washington.

"In light of recent 737 crashes in Indonesia and Ethiopia, the committee is investigating any potential connection between inadequate training and certification of Aviation Safety Inspectors who may have participated in the FSB evaluation of the 737 MAX," Sen. Roger Wicker, R-Miss., chairman of the committee, wrote to FAA Acting Administrator Daniel Elwell on Tuesday.

The Senate Commerce Committee is launching a probe into whistleblower complaints accusing the Federal Aviation Administration of improperly training its safety inspectors to review the Boeing 737 Max jets.

"Allegations from these whistleblowers include information that numerous FAA employees ... had not received proper training and valid certifications."

Wicker said that the FAA may have been notified about these deficiencies as early as August 2018 and that an agency investigation into the allegations may have already been completed.

In response to a CNBC request for comment, the FAA cited Elwell's statement at a Senate Commerce Committee hearing last week: "In our quest for continuous safety improvement, the FAA welcomes external review of our systems, processes, and recommendations," he said.

Boeing's 737 Max jets have been grounded worldwide for more than two weeks. The company is currently working on a software fix for the plane's flight-control systems after two crashes of Max jets in Indonesia and Ethiopia killed a total of 346 people.