US officials, speaking on condition of anonymity, said Hassan Ali Dhoore and two others were killed in the airstrike in southern Somalia, close to the Kenyan border.
"We have been watching him off and on for a long time," one official told the AFP news agency.
The military said it was still assessing the results of the strike, which was carried out on Thursday.
Dhoore was allegedly part of al-Shabab's security and intelligence wing. He had been involved in planning attacks in Mogadishu, including an assault on the capital's airport that killed at least nine people on Christmas Day in 2014, the Pentagon said in a statement. He was also allegedly "directly responsible" for a March 2015 attack on a Mogadishu hotel, resulting in the deaths of 15 people, the statement read.
Pentagon spokesman Peter Cook said "removing Dhoore from the battlefield would be a significant blow to al-Shabab's operational planning and ability to conduct attacks."
This week's strike comes less than a month after US drones killed more than 150 al-Shabab fighters at a Somali training camp. The militant group, which is affiliated with al Qaeda, has launched several attacks on government and international targets in a bid to impose its strict version of Sharia law in the region. The group was also behind an attack on Kenya's Garissa University in 2015, which killed nearly 150 people.
Somalia descended into chaos in 1991 when armed opposition groups brought down the military-style government of the late President Siad Barre.
nm/jlw (Reuters, AP, AFP)