The National Labor Relations Boards pursuit of the Boeing Co. for alleged unfair labor practices came to an abrupt end on Friday as the federal agency approved the withdrawal of charges by the machinists union against the aerospace giant.

The federal agency had charged Chicago-based Boeing with illegally transferring work on its 787 Dreamliner to a new South Carolina facility in retaliation for past union strikes at its Washington state production site. Boeing has steadfastly denied the accusation since April, when the NLRB first issued the complaint.

The International Association of Machinists and Aerospace Workers asked to withdraw the charges following the ratification of a four-year collective bargaining agreement between its members and Boeing earlier in the week, according to NLRB Acting General Counsel Lafe Solomon. That agreement assures assembly of the modernized 737 remains in Washington state.

"This is the outcome we have always preferred, and one that is typical for our agency," said Solomon in a statement.

Solomons prosaic statement following the conclusion of the high-profile case belies the strong emotions and controversy that have accompanied it from the start -- and which have seen the agency come under intense scrutiny.

Indeed, Darrell Issa, R-Calif., chairman of the House Committee on Oversight & Government Reform, made clear that the conclusion of the Boeing case would not end his committees investigation of the NLRB.

"NLRB's record of rogue action and lack of transparency with the public and Congress in this case -- and in others -- has raised serious questions that remain unanswered," Issa said in a statement.

Issa has been seeking documentation from the NLRB regarding its decision-making process in the Boeing case, claiming the agency has been less than forthcoming. In August he charged the board with failing to comply with a federal subpoena, a charge the NLRB denied.

The close of the Boeing case should end the agencys reluctance to turn over materials, Issa said.