A Western official said there was also reason to believe that al Qaeda’s core leadership was involved in orchestrating subsequent failed plots against European and U.S. targets.

One of the plots that US officials believe bin Laden was at least aware of was a 2006 plot to bomb multiple US-bound transatlantic airline flights using home-made liquid explosives.

The plot was disrupted when British authorities launched a major roundup of suspects. Flights to and from Britain were severely disrupted and tight new restrictions were placed on passenger carry-on items such as liquids and gels.

US and European officials also believe that al Qaeda “senior leadership” supervised a 2009 plot, led by an Afghan immigrant, to bomb New York’s subway system. That plot was disrupted when U.S. authorities arrested the alleged mastermind, Najibullah Zazi, and a handful of associates.