This week’s report of a downed US pilot’s encounter with “jellyfish drones” in the skies over Iran set off a vigorous defense debate — and foreshadows future dangers.

A source told CNN that the F-15 pilot described seeing “multiple drones interconnected and moving as one, with smaller drones below the bigger drones like legs” before the jet crashed near the Zagros Mountains.

“Real alien sh-t,” as the pilot put it.

But experts are divided about what exactly the pilot saw, and whether it represents a new type of threat.

The description is highly reminiscent of previous sightings of what looked like giant aerial jellyfish over both Iraq and Afghanistan.  

One of these, filmed near Al Taqaddum Air Base in Iraq in 2017, was originally reported as a UFO — but a Pentagon investigation concluded that it was a cluster of metallic balloons.

Another video, apparently taken by a Reaper drone in Afghanistan in 2024, showed a similar multi-balloon arrangement — a sight so weird that some took it to be a UFO, but on closer examination turned out to be entirely earthly.

Many militaries use balloons — sometimes single huge weather balloons, sometimes clusters or trains of smaller balloons — to carry sensors for intelligence-gathering purposes.

Perhaps the most famous example of this is 1947’s Project Mogul, a highly classified US effort aimed at detecting the stratospheric echoes of Soviet nuclear tests.

When debris from a Project Mogul balloon train was found near Roswell, NM, the military initially claimed it was a crashed flying saucer — spawning an entire industry that’s still going strong.

Those recently spotted Middle East jellyfish balloon clusters were likely carrying electronic surveillance devices or other sensors, and may have been of Iranian origin.

But given the F-15 pilot’s specific mention of drones, we shouldn’t dismiss this sighting as a balloon cluster, despite the obvious similarity.

A lot is riding on the word “interconnected” in the service member’s testimony.

If it means the drones were physically interconnected with wires strung between them, this sounds like a reinvention of the barrage balloon concept used to protect cities in World War II.

These giant tethered blimps were strung together with wires, creating an impassable obstacle to low-flying bombers.

A similar arrangement using drones could create an airborne barrier against incoming aircraft and cruise missiles.

However, “interconnected” could refer to electronic links that had the drones flying in formation in a giant jellyfish-like shape.

That’s simple enough for light-show drones: Thousands of them, pre-programmed and with a central controller, can form shifting shapes of symbols, dragons, words or anything else — including, yes, jellyfish.

The type of controls used by light-show drones are easily jammed, so they’re impractical in a military environment.

But many militaries, including the US, Ukraine and Russia, are working on swarming drone capabilities, typically using secure mesh radio systems.

In a swarm, a group of autonomous drones work together and fly in formation without the need for the central control and planned choreography light-show drones require.

The F-15 pilot also described an apparent “minefield of drones” in the air, which aligns with the WWII barrage balloon tactic.

Armed drones are much too slow to catch an agile jet fighter — but a mass of them spreading out can cover a large section of the sky.

A jet flying through the formation risks catastrophic damage if it gets close to one that detonates.

In 2021 Russian drone maker ZALA described using wide-spaced interceptor drones to create an aerial minefield impossible to pass through, though there’s no evidence the company pushed forward with this idea.

Some have suggested that the pilot, who suffered a concussion in the crash, must have been mistaken about what he saw.

This would certainly be convenient.

But the Iranians have a long history of military drone development, and Tehran has become a major drone exporter.

The thousands of Shahed drones that Russia flings at Ukraine’s cities were designed in Iran.

And the regime is certainly not ignorant of swarms: In 2021 the Iranian Army showcased a new system it called Mass Flight, in which an operator controls a leader drone with a squadron of nine additional drones automatically following its lead.

This was described as having “counter air capability,” meaning it could be used against aircraft.

The technology was crude at the time, but it may have advanced significantly in the last five years.

Crucially, we still don’t know if whatever the F-15 encountered was actually related to the downing of the aircraft: did the pilot run into a drone?

Or was he distracted enough to miss another threat? Or was this sighting simply a bizarre incidental feature of the mission?

At present we have more questions than answers.

Only the Iranians know the truth — and they’re not telling.

David Hambling is the author of “Swarm Troopers: How Small Drones Will Conquer the World.”