(Reuters) -Proxy advisory firm Glass Lewis on Tuesday recommended shareholders vote against the election of three directors - Dave Calhoun, Akhil Johri and David Joyce - to planemaker Boeing's ( BA ) board.

Boeing ( BA ) was not immediately available for a comment. Calhoun has said he will step down as CEO of the embattled planemaker at the end of the year.

Johri and Joyce serve as chairs of the Boeing ( BA ) board's audit and aerospace safety committees, respectively.