The airspace in Southern California is busy and complex, and according to the National Air Traffic Controllers Association (NATCA), a staffing crisis is eroding the margin of safety to "dangerously low levels." A shortage of qualified staff is forcing many controllers to work overtime and six-day weeks, while more controllers are retiring and new hires are not being trained quickly enough, NATCA said on Tuesday. FAA spokesman Ian Gregor disputed NATCA's claims, telling NBC4.tv that the agency is actively training new recruits and planning for retirements. He acknowledged, however, that Long Beach controllers are working overtime. He said the FAA will bring five new hires on board in the next year. NATCA said continuing staff shortages could cause delays at Los Angeles International Airport, as well as result in higher numbers of runway incursions and controller errors. NATCA says the rate at which new hires can qualify as fully trained is inadequate to replace the coming wave of retirements of veteran controllers.