Ibrahim Hassan al-Asiri: the prime bombmaking suspect
Ibrahim Hassan al-Asiri, a Saudi who is regarded as a key member of al-Qaida's operation in , is the prime suspect for constructing the two bombs.
The 28-year-old son of a retired soldier, Asiri is seen by US intelligence as the primary bombmaking expert for al-Qaida in the Arabian Peninsula, having constructed the "underpants bomb" used in the failed suicide attack by a Nigerian on an airliner over Detroit on Christmas Day.
He is also regarded as among the most fanatical al-Qaida adherents after dispatching his 23-year-old brother, Abdullah, on a suicide mission to kill Saudi Arabia's security chief, Prince Mohammed bin Nayef, by hiding a bomb in a body cavity. Nayef survived with minor injuries, but Abdullah al-Asiri died.
US officials believe Asiri is working closely with the radical US-born cleric Anwar al-Awlaki, who has provided the "spiritual" support for attacks on the US as well as being a driving force behind them.
Both men are primary targets for CIA assassination attempts using drones or other air attacks.
Asiri was first named on a Saudi Arabian wanted list in February 2009. Not much is known about his early life, other than that he comes from a pious family.
His father, Hassan, told the Saudi Gazette last year: "We were planning to move back to Riyadh, but Abdullah and Ibrahim said they wanted to go to [the holy city of] Medina before returning with us.
"Abdullah later contacted us to say he was out of the country, but did not say where. From that day on we had no more news of him until we saw his and his brother's pictures … in the media on a list of wanted people."
Although his bombs are not always sophisticated, the construction of the two devices shipped on cargo planes suggests Asiri is becoming better at shielding them from detection.