Until now, Israel has kept its drone program secret -- refusing to even acknowledge that it uses them in warfare.
But now there's photo evidence from the drones themselves.
The images come from classified material in documents exposed by former U.S. National Security Agency contractor Edward Snowden.
CNN has reviewed the documents published by The Intercept, but the NSA, following agency policy, does not verify the authenticity of its exposed files.
The American and British spying are part of regular, ongoing international espionage. The United States and Israel, although allies, regularly peek in on each other's military projects, according to several former U.S. national security officials.
To operate by remote control, large military drones send a signal to satellites in space. Spies at the NSA and the British Government Communications Headquarters managed to capture those signals and decode them, according to these documents.
GCHQ would not acknowledge the documents. Instead, it provided its standard statement assuring its actions are legal, reviewed by officials, and abide by human rights laws.
Neither the NSA nor the Israeli Embassy provided a comment for this story.
"It is a longstanding policy that we do not comment on intelligence matters," the agency told CNN.
As far back as 2009, spies were able to track the locations of Israeli drones, see video feeds from them and even watch what the drones were targeting, according to the documents.
For a six-month period sometime before 2012, American spies monitored "regular" flying missions of an Israeli-made Heron TP, a large twin tail drone that was "carrying weapons," according to the NSA documents.
American and British spies did not hack the drones or hijack their controls. Instead, spies simply captured the signal between the drone and satellite. But they did have to hack to decode the signal, documents show.
Hacking turned the scrambled signal from fuzzy gray screen into a clear picture of a drone's wing, or landing gear, or even the buildings and people targeted miles below.
Israel uses its military drone program to target Islamic militants in the Gaza Strip, similar to U.S. drone strikes on suspected terrorists. Watchdog groups such as Amnesty International and Human Rights Watch have expressed concerns about collateral damage, investigating dozens of Israeli drone strikes in 2008 and 2009 that killed up to 87 civilians in Gaza during wars between Israel and Hamas.
According to one document, hackers at NSA and GCHQ were able to decode the videos using publicly-available software. This shows that Israeli drones are not using a robust system to encrypt these signals.
But getting real-time, immediate video feeds from Israeli drones is a difficult feat, the documents stated.
Documents indicate that spies were able to capture the Israeli drone signals from a British military outpost in the island of Cyprus.
Israeli drones weren't the only things that were spied on. In at least one instance, American spies were able to tap into the video feed of an Israeli F-16 fighter jet, documents show.
They were also able to spy on an Iranian-made drone that was being launched from a Syrian Air Force base in early 2012, just as President Bashar Al-Assad's government escalated its attacks on protesting civilians as the Syrian civil war intensified.
The NSA documents say there was "presidential level interest in further video samples," indicating that the White House wanted to closely watch Assad's military campaign against his own citizens.
