On this day ten years ago, President George Bush was back in the White House from a vacation in Texas, where he had been briefed about a CIA report titled, "Bin Laden Determined to Strike in the U.S."
On the same day, half a world away in Afghanistan, al Qaeda leader Osama Bin Laden received word that the date of that strike had been finalized: Sept. 11.
Some of the 19 hijackers who would fly planes into the Pentagon and the World Trade Center were working out at their local gyms, focusing on kickboxing and self-defense. Some prepared to wire unused cash back to al Qaeda bank accounts in the Middle East.
One of the hijackers, Mohand al-Shehri, called United Airlines on September 6, 2001 to correct the spelling of his name on his Sept. 11 reservation.
All 19 of them were in the United States on legal visas issued in their true names, with no real background checks.
"There were so many loopholes," said Mary Schiavo, the former Inspector General of the Department of Transportation. "There was little chance the hijackers would be caught on September 11."
Ten years later, authorities have taken multiple measures, from transforming airport security to tightening immigration controls, to avoid a repeat of the attacks that left 3,000 dead in New York, Virginia and Pennsylvania.
Richard Clarke, a former counterterrorism official and now an ABC News consultant, said that in 2011, "It's very, very hard to get a visa to enter the United States if your name even sounds like a terrorist."
At Boston's Logan Airport on this day ten years ago, two hijackers arrived from Florida, and later others were seen casing the security they would pass through easily on Sept. 11 carrying boxcutters and knives.
At the time, airport security was run by the airlines themselves. The federal government created the Transportation Security Administration soon after the 9/11 attacks, and today employs tens of thousands of screeners.
"Now it's different," says Schiavo, "because we have a professional law enforcement agency responsible for security."
However, as the Government Accountability Office has found, TSA equipment still can't reliability detect explosives, and TSA screeners continue to somehow miss a huge number of guns and weapons at airport security posts.
Clark Kent Ervin, former Inspector General of the Department of Homeland Security, said, "We don't pay them very much money and we don't train them very well. And that is what you get."