April 17 (Reuters) - Boeing's ( BA ) manufacturing

practices, at the center of a full blown safety crisis following

a Jan mid-air panel blowout, will come under scrutiny on

Wednesday in two U.S. Senate hearings.

Boeing ( BA ) has been grappling with a crisis that has undermined

its reputation following the Jan. 5 mid-air panel blowout on a

737 MAX single-aisle plane. It has undergone a management

shakeup, U.S. regulators have put curbs on its production, and

deliveries fell by half in March.

The U.S. Senate Commerce Committee is holding a hearing

with members of an expert panel that released a report in

February criticizing the planemaker's safety culture and calling

for significant improvements.

A later session is expected to feature testimony and

documents from Boeing ( BA ) whistleblower Sam Salehpour, a current

engineer at the company, his lawyers said.

Salehpour has claimed that Boeing ( BA ) failed to adequately shim,

or use a thin piece of material to fill tiny gaps in a

manufactured product, an omission that could cause premature

fatigue failure over time in some areas of the Boeing 787

Dreamliner.

Boeing ( BA ) has challenged Salehpour's claims against two of its

widebody jets, the 787 and 777, which fly internationally.

Boeing ( BA ) said on Monday it has not found fatigue cracks on

in-service 787 jets that have gone through heavy maintenance.