By the CNN Wire Staff March 11, 2011 6:52 a.m. EST Washington (CNN) -- The Federal Aviation Administration ordered the nation's airlines to remove emergency oxygen masks from the restrooms on some 6,000 planes last month, but it only made the work public this week. "In order to protect the traveling public, the FAA eliminated the problem before making the work public," FAA said is a statement Thursday. "Had the FAA publicized the existence of this security vulnerability prior to airlines fixing it, thousands of planes across the U.S. and the safety of passengers could have been at risk." The FAA didn't say what the risk was or what triggered the concerns. According to the agency, it is working with aircraft manufacturers to design, certify and install a new oxygen system for restrooms in all types of aircraft in the U.S. fleet. Until then, flight attendants have been told "to make it a priority to check whether the lavatory is occupied following any event where oxygen masks are deployed in the cabin."