Southwest Airlines begins flying first plane with secondary cockpit barrier

(Reuters) -Southwest Airlines began Friday flying its first jet with a secondary barrier to the flight deck designed to prevent intrusions. The plane - a Boeing 737 MAX 8 which was delivered in recent days - took off Friday afternoon from Phoenix to Denver, the airline said. Secondary barriers -- long sought after the Sept. 11, 2001 attacks that exposed the risks of inadequate flight detect protection -- are crucial to aviation safety, pilots unions have argued.