The FAA announced on 11 August 2008 that it would investigate why "almost half the masks either did not deploy or failed to provide oxygen" during a pan-pan event on American Airlines Flight 31[15] The FAA had recently issued airworthiness directives regarding problems with defective inline flow indicators obstructing the BE Aerospace oxygen masks on several Boeing commercial aircraft models. B/E had identified a repair in February 2006. Boeing then issued a "Special Attention Service Bulletin" to inspect and if necessary repair the masks in April 2007.