Emirates Airlines revealed on Wednesday that New York suspect Faisal Shahzad had bought one-way ticket to Islamabad.
Faisal Shahzad, who was arrested late on Monday for a botched terror attack in New York, was charged on five counts, including attempting to use weapon of mass destruction.
During interrogation, Shahzad admitted having attended a militant training camp in Waziristan. He bought a sports utility vehicle that was found loaded with an improvised explosive device in Times Square.
Investigators said that the Connecticut resident has implicated himself and told them he was acting alone.
Interior Minister Rehman Malik said that Shahzad has a Karachi identification card although his family is from the Pabbi area in Khyber Pakhtunkhwa.
Two people thought to have been in contact with Shahzad, have also been detained in Karachi.
Shahzad was arrested on a Dubai bound plane at JFK airport late on Monday, two days after the car bomb was found.