Janitors at Boeing, Raytheon and Northrop Grumman facilities will walk off the job Wednesday night to protest what they call unfair labor practices, according to union officials...Union officials said the janitors backed a strike after cleaning companies reportedly "threatened, harassed and fired workers to keep them quiet about poverty conditions." Dick Davis, a representative for Somers Building Maintenance -- one of the companies that provides janitors for Boeing...noted that there have not been any credible charges filed against any of the aerospace companies alleging unfair labor practices. Boeing spokesman Eric Warren said the company respects the janitors' rights "to peacefully assemble and make their feelings known, but the issues they have aren't with Boeing, but with our third-party contractor."...Tim Henson of Northrop Grumman also said no disruptions were expected. Officials at Raytheon could not be reached for comment. [also refers to Aramark]