President Barack Obama's security teams briefed the vacationing president on threats facing the United States and he directed that heightened airport security measures remain in place as officials investigate a failed terror attack aboard a Detroit-bound plane.

Officials, meanwhile, pondered a formal inquiry into what changes might be needed for U.S. intelligence operations that allowed the suspect to be purged from a massive and broad government database of potential threats.

White House officials began their Saturday at 4 a.m. in Hawaii _ 9 a.m. on the clock in Washington _ to prepare with counterparts across the government a briefing for Obama. National Security Council chief of staff Denis McDonough in Hawaii, homeland security and counterterrorism adviser John Brennan and others in Washington spoke with Obama at 6:20 a.m. by secure telephone conference call at the first family's rented vacation home.

The call lasted less than 15 minutes. Obama left immediately afterward for a trip to the gym.

Other traveling administration aides also were kept in a secure hotel room to receive briefings from investigators, to monitor developments, to feed updates to the president and to coordinate across agencies. Regular updates were sent to the president, who _ despite being on holiday _ made decisions to continue increased security precautions he put in place after Friday's incident.

As Obama spent more than six hours on a Marine Corps golf course, his national security and policy advisers asked each other and peers questions such as: How is the intelligence community integrating itself? Did the assumptions used to make terror watch list choices lead to the correct decisions? Were the right criteria used to reach conclusions?

The officials described the early discussions Saturday on the condition of anonymity so as not to pre-empt possible official announcements that could come as early as Sunday and to discuss sensitive materials.

Such internal questions among Obama's team marked the informal start to what would likely become a formal executive branch inquiry into an attack that failed _ not because of the intelligence community but because, it appears, the suspect's material failed to ignite.

On Friday, officials said a man tried to blow up a plane as it prepared to land in Detroit before nearby passengers _ who saw a glow and heard what sounded like firecrackers _ tackled him. The Justice Department on Saturday charged that Umar Farouk Abdulmutallab willfully attempted to destroy or wreck an aircraft; and that he placed a destructive device in the plane.