Details of a planned US airstrike in Yemen mistakenly shared with a journalist on the messaging app Signal were almost certainly classified information, military experts say, despite the White House declaring otherwise.

The Atlantic magazine published the messages this week after the magazine’s editor-in-chief, Jeffrey Goldberg, was inadvertently added to a group chat involving a host of Trump administration officials in the days before the planned strike on March 15. Goldberg received an invitation from national security adviser Mike Waltz to join the group on March 11 and was part of the group as it discussed details of the strike hours before it happened.

An aircraft flies from the USS Harry S Truman in the Red Sea before airstrikes in Yemen on March 15.Credit: AP

The revelation that highly sensitive attack plans had been shared on a commercial messaging app, possibly on personal mobile phones, has triggered outrage in Washington and calls from Democrats for members of President Donald Trump’s national security team be fired over the leaks.

Defence Secretary Pete Hegseth has repeatedly denied texting any war plans in the group chat and Trump and his top advisers are saying no classified information was shared, but that has bewildered Democrats and former US officials, who regard timing and targeting details of an airstrike as some of the most closely held material ahead of a US military campaign.

Vice President JD Vance, CIA director John Ratcliffe and national intelligence director Tulsi Gabbard were also part of the Signal chat that included Goldberg.

‘We are GO for mission launch’

Military experts have said the information included in this message would definitely be classified.

Philip Ingram, a former military intelligence officer with the British Army, told the BBC it would be deemed top secret. “You can practically plot where the aircraft are going to come from,” he said.