A senior Qaeda militant in Yemen linked to the deadly bombing of an American warship there in 2000 was killed in an airstrike on Sunday, the Yemeni government said, in the latest sign of an escalating American campaign to counter the terrorist threat there. Yemeni authorities said the militant, Fahd Mohammed Ahmed al-Quso, 37, who has been on the F.B.I.’s Most Wanted list in connection with the bombing of the Navy destroyer Cole that killed 17 sailors in October 2000, died in the strike in Shabwa Province in one of the rugged tribal areas controlled by insurgents. The Yemen Embassy...