Israel’s top cyber hacking operations against the Islamic State (ISIS) led to the discovery that a small cell of bombmakers in Syria was planning to down planes using sophisticated laptop bombs.

The New York Times reported the discovery of the crucial intelligence, later leaked by U.S. President Donald Trump to the Russians, and one of the few successes achieved in cyber intelligence efforts against ISIS.

According to unnamed officials the quality of the intelligence was such that the U.S. was able to discern how the devices would be detonated. The cell of ISIS bombmakers had designed the explosives to fool airport X-ray machines so they appeared to be batteries for laptop computers.

Read more: U.S. officials ‘warned Israel’ not to share sensitive intel with Trump

Ten airports across Jordan, Egypt, Kuwait, Morocco, Qatar, Turkey, Saudi Arabia and the U.A.E. were placed under enhanced security measures that banned laptops, and other items on the grounds of the intelligence in March following a directive by the Department of Homeland Security.

The department also briefly considered extending the ban across Europe given the seriousness of the threat.

The closely-guarded intelligence became public knowledge when, according to the Washington Post, Trump disclosed details about the plot during a meeting in May with Russian Foreign Minister Sergei Lavrov and Russian ambassador Sergey Kislyak.

Laptop threat An illustration picture shows a laptop on the screen of an X-ray security scanner, April 7, 2017. The classified information Trump allegedly gave to Russian officials reportedly related to an ISIS plot connected with aviation security. The U.S. recently introduced a laptop ban on inbound U.S. flights from several Middle Eastern countries. Srdjan Zivulovic/Reuters

It later emerged the intelligence had come from Israel, although it was originally believed it had been gleaned through human sources on the ground rather than hacking operations. Both the U.S. and Israel talked down the impact of the leak on intelligence sharing operations in the run-up to Trump’s visit to Israel only days later.

The New York Times reported that U.S. cyber operations have had limited success in disrupting ISIS’ online operations in the past 12 months. Since the Pentagon announced a new line of cyber combat against the militant group in 2016, the mission has faltered in stopping ISIS from spreading propaganda online, finding new recruits, paying its fighters and sending out orders.

This is largely the case because ISIS has the ability to quickly re-establish communications hubs as soon as they go down.  

Joshua Geltzer, who was the senior director for counterterrorism at the National Security Council until March, said there had been disappointment over the operations.

“This is just much harder in practice than people think. It’s almost never as cool as getting into a system and thinking you’ll see things disappear for good,” he said.