CAIRO – A Saudi militant believed killed in the U.S. drone strike Friday in Yemen built the bombs for the al-Qaida branch’s most notorious attempted attacks — including the underwear-borne explosives intended to a down a U.S. aircraft, and a bomb carried by his own brother intended to assassinate a Saudi prince.

The death of Ibrahim Hassan al-Asiri would make the Friday drone strike on a convoy in the central deserts of Yemen one of the most effective single blows in the U.S. campaign to take out al-Qaida’s top figures.

The strike also killed Anwar al-Awlaki, a Yemeni-American cleric who had been key to recruiting for the militant group, and Samir Khan, a Pakistani-American who was a top English-language propagandist.

But Christopher Boucek, a scholar who studies Yemen and al-Qaida, said al-Asiri’s death would “overshadow” that of the two Americans due to his operational importance to al-Qaida in the Arabian Peninsula, the Yemen-based group that is considered the most active branch of the terror network.

Late Friday, two U.S. officials said intelligence indicated al-Asiri was among those killed in the strike. The officials spoke on condition of anonymity because al-Asiri’s death has not officially been confirmed.

Al-Asiri, 29, was one of the first Saudis to join the Yemen-based al-Qaida branch and became its key bombmaker, designing the explosives in two attempted attacks against the United States.

His fingerprint was found on the bomb hidden in the underwear of a Nigerian accused of trying to blow up Northwest Airlines Flight 253 over Detroit on Dec. 25, 2009, according to U.S. counterterrorism officials. The attack failed because the would-be bomber, Umar Farouk Abdulmutallab, botched detonating the explosives, burning only himself before being wrestled away by passengers.

The explosives used in that bomb were chemically identical to those hidden inside two printers shipped from Yemen last year, bound for Chicago and Philadelphia in a plot claimed by al-Qaida. The bombs were intercepted in England and Dubai.

In perhaps his most ruthless operation, al-Asiri turned his younger brother, Abdullah, into a human bomb in a 2009 attempt to kill Saudi Prince Mohammed bin Nayef, the kingdom’s top counterterrorism official and son of its interior minister.

Abdullah volunteered for the suicide mission, according to Sada al-Malahem, an Arabic-language Web magazine issued by al-Qaida in the Arabian Peninsula.

Abdullah pretended he was surrendering to Saudi authorities, and Prince Mohammed agreed to receive him in his home in Jiddah during a gathering to celebrate the Muslim holy month of Ramadan.

While talking to the prince, Abdullah blew himself up. The prince, however, escaped with only injuries.

Saudi officials have said the bomb was “inside” Abdullah’s body, but explosives experts believe al-Asiri strapped the bomb between his brother’s legs.

All three bombs contained a high explosive known as PETN, or pentaerythritol tetranitrate, which was also used by convicted shoe bomber Richard Reid when he tried to destroy a trans-Atlantic flight in 2001.