U.S. air crash investigators, who are assisting in probes of two fatal crashes of Boeing Co.’s (BA.N) grounded 737 Max, plan to issue recommendations within 60 days on how the plane was designed and certified.

National Transportation Safety Board Chairman Robert Sumwalt revealed the agency’s intention Wednesday at a Senate Commerce Committee hearing. The board will issue a recommendation package on “design certification issues,” Sumwalt said.

Details of what the safety board will call for in the package weren’t revealed.