Two C-130 aircraft were lost during the operation, an official said.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israeli strikes attack targeting military and government sites, officials said.
Watch special coverage on Nightline, "War with Iran," each night on ABC and streaming on Disney+ and Hulu.
The Israel Defense Forces said in a post to X on Monday that it launched fresh strikes on the Lebanese capital Beirut targeting what it said was Hezbollah infrastructure.
President Donald Trump said in a post to social media that the U.S. struck "many long sought after targets" in Iran on Sunday.
"Big day in Iran. Many long sought after targets have been taken out and destroyed by our GREAT MILITARY, the finest and most lethal in the World," Trump wrote.
Earlier on Sunday, Trump reportedly told the Financial Times that the U.S. has about "3,000 targets left -- we've bombed 13,000 targets."
Trump also suggested to the FT that he is considering a ground operation in Iran, possibly aimed at Iran's Kharg Island oil export terminal in the northern Persian Gulf. Trump said U.S. forces could "very easily" take the island.
"Maybe we take Kharg Island, maybe we don't. We have a lot of options," Trump told the FT, noting that this would "mean we had to be there for a while."
"To be honest with you, my favourite thing is to take the oil in Iran but some stupid people back in the U.S. say: 'Why are you doing that?' But they're stupid people," Trump told the FT.
The administration is reportedly considering a ground operation against Iran in the Persian Gulf to safeguard the strategic Strait of Hormuz, where commercial shipping has been subject to Iranian harassment and tolls since the U.S. and Israel launched the conflict on Feb. 28.
Trump told reporters on Air Force One on Sunday that Iran had given permission for 10 oil tankers to pass through the Strait, and that another 20 more would do so soon.
Speaking to the FT, Trump claimed that Iran's Parliament Speaker Mohammad Bagher Ghalibaf was "the one who authorized the ships" to pass through safely.
Trump also again speculated about the status of Iran's newly-appointed Supreme Leader Mojtaba Khamenei, who succeeded his father Ayatollah Ali Khamenei after the latter was killed by U.S.-Israeli airstrikes on Tehran on Feb. 28.
"The son is either dead or in extremely bad shape," Trump said. "We've not heard from him at all. He's gone."
Mojtaba Khamanei's absence from the public eye has fueled speculation he was badly injured in the American-Israeli attacks, though Tehran has insisted he is alive and safe.
-ABC News' Meg Mistry and Emily Chang
The Lebanese Ministry of Public Health said in an update on Sunday that 1,238 people have been killed since the start of the war in Lebanon, with 3,543 people injured.
The health ministry said 49 people were killed on Sunday, with 116 injured.
A United Nations peacekeeper was killed over the weekend "when a projectile exploded in a UNIFIL position" in Southern Lebanon, according to the organization. Another peacekeeper was critically injured.
UNIFIL, the U.N. Interim Force in Lebanon, said it does not know where the projectile originated from, and an investigation is ongoing.
"Too many lives have been lost on both sides of the Blue Line in this conflict. There is no military solution. The violence must end," UNIFIL said.
-ABC News' Victoria Beaulé
