Tools and components used to repair a plane’s oxygen system must be cleaned in a particular way to remove any residue that could react when it comes into contact with oxygen, the report noted. If left unchecked, a contaminated oxygen system could increase the risk of fire or even cause an explosion. In a written statement, Boeing told CNN  that last year’s mishap did not result in any injuries and the aerospace contractor paid for the damages. “Boeing fully understands the level of responsibility that comes from working on the President’s aircraft.”