The full force of the U.S. is now targeted on Ibrahim al-Asiri, the young Saudi bombmaker believed to be behind the two bombs found Friday in UPS and FedEx packages bound from Yemen to Chicago.
Asiri, 28, also said to have been behind last year's attempted Christmas bombing of Northwest flight 253, continues to outmatch billions of dollars in airport security equipment and presents a clear and present danger.
"We need to find him," said John Brennan, President Obama's top antiterrorism advisor.
American officials now concede that Asiri's two latest bombs would have made it onto flights to the U.S. but for the Saudi intelligence service providing the parcel tracking numbers.
Said Homeland Security Secretary Janet Napolitano, "We were able to identify by where they were emanating from and package number, where they were located."
The bombs were cleverly disguised inside Hewlett-Packard printers being shipped along with clothes, books and a tourist souvenir.
Asiri packed the toner cartridge with explosives and added the circuit board of a cell phone--something that did not stand out in state of the art cargo screening.
"We're dealing with an ever changing, ever-evolving threat," said Napolitano.
While the packages were addressed to two synagogues in Chicago, US officials now agree with an initial British estimate that the UPS and FedEx cargo planes that were to carry the parcels over the Atlantic were the real targets of the plot.
"At this point," said Brennan, "we, I think, would agree with the British that it looks as though they were designed to be detonated in flight."
The cell phone trigger would have made it possible to detonate the cargo bombs as the planes approached or flew over an American city.
"It would cause catastrophic damage, it would send debris all over the cities" said Kevin Barry, a former NYPD bomb squad detective now with the International Association of Bomb Technicians and Investigators. "There's also a flight crew on that plane too."
Authorities in Yemen have released on bail a 22-year-old female engineering student whose name and phone number were on the shipping documents for the two bombs sent to the United States.
A lawyer for Hanan Samawi told ABCNews.com that the young woman had returned home after being held and questioned.
The lawyer said Samawi's father had been instructed to have his daughter avoid news reporters.
A Yemeni official briefed on the investigation said the suspect "is not allowed to leave the country pending further questioning."
The official said the shipping agent who received the packages was called in to identify her and said Samawi "was not the person who signed the shipping manifesto."
The official said authorities now believe it is a case of "stolen identity by an individual who knew the detained suspect's full name, address and telephone number."
Her arrest had been trumpeted by the President of Yemen, Ali Abdullah Saleh, as evidence of its cooperation with the U.S. and others to combat terrorism.
But as her fellow students mounted a protest Sunday at a university, her lawyers questioned why anyone involved in the plot would use their real name and phone number to ship a bomb.