The Senate Commerce Committee is investigating whistle-blower claims that Federal Aviation Administration safety inspectors who evaluated Boeing’s 737 Max airplane were not appropriately trained or certified.

[Boeing Congressional Hearing: F.A.A. warned of 737 Max’s safety before second crash.]

On Tuesday, the committee chairman, Senator Roger Wicker, Republican of Mississippi, sent a letter to the F.A.A. demanding information about whether the agency had investigated those allegations or taken any action to remedy the problem.

After the fatal crashes of two 737 Max jets in less than five months, there is new scrutiny on the regulator’s close relationship with Boeing. The F.A.A. relies on Boeing employees to help certify the airworthiness of its aircraft, a system that critics say creates conflicts of interest.

In hearings last week, lawmakers pressed Elaine L. Chao, the transportation secretary, and Daniel K. Elwell, the acting administrator of the F.A.A., about federal oversight of aviation safety. Federal prosecutors are investigating the development of the Max plane, which included new software that may have contributed to the fatal accidents.