The steady flow of military assets moving towards Europe and the Middle East appeared to be a warning that the US could be ready to attack Iran.
This visualisation shows the movement of some US military aircraft flying from North America to air bases in Europe and the Middle East from January 13 until February 10 — only weeks before the US launched its attack targeting Iran on February 28.
The data from tracking website Flightradar24 showed the movement of two heavy transport planes — the Lockheed C-5M Super Galaxy and the Boeing C-17A Globemaster III.
These aircraft can be used to move US assets.
It also showed the Boeing KC-135R Stratotanker — an aerial refuelling plane needed to help aircraft like fighter jets make the trip across the North Atlantic.
The period of time tracked by the ABC started when President Donald Trump told Iranians via Truth Social on January 13 that "help is on its way" as many took to the streets to protest the country's regime.
This was just some of the aircraft that made the trip, as the data was only from flights that had tracking systems turned on.
Late last week, plane tracking experts noted many aircraft leaving the US or repositioning from Europe into the Middle East.
Steffan Watkins, a researcher who tracks ships and aircraft using open-source information, said February 18 had been one of the most active periods of movement during the previous month.
"They seem to have much of, if not all they need for a large-scale attack, or to defend Israel from retaliation," he said at the time.
Crucially, E-3 Sentry airborne warning and control systems (AWACS) — distinctive aircrafts with radar domes perched on the plane body — began being tracked on February 17 leaving the US.
Mr Watkins said similar aircraft movements happened before Operation Midnight Hammer — the attack last year which saw US bombers hit Iranian nuclear sites.
"It's unclear to me whether the E-3 Sentry was clearing the way or acting as an escort," Mr Watkins said.
"There have been dozens of these flights coming over to various American bases and it looks like very much the same as what happened last time during Midnight Hammer," he said, speaking more generally about the movement of aircraft.
More aircraft spotted
Commercial satellite imagery showed a build-up of aircraft in various US-linked bases in the Middle East.
This image of Al Udeid Air Base in Qatar, taken on February 1, showed aerial refuellers, transport aircraft and a reconnaissance aircraft on the apron.
Mr Watkins said tracking the aircrafts' departure location could give clues as to what they were carrying.
"Exactly what they're carrying, we don't really know, but we know where they took off," he said.
"A lot of the places that they took off from have anti-aircraft batteries or divisions, units that handle anti- air."
Air defence systems had also been seen appearing in satellite imagery at Al Udeid.
Aircraft carrier USS Abraham Lincoln was also spotted in satellite imagery in the Arabian Sea on February 15 — the first time it had been seen since its arrival in the Middle East in January.
US media reported another aircraft carrier, USS Gerald R. Ford, was also on its way to the region.
"I think it's also important to recognise that we have a significant amount of air defence capabilities on some of the ships that we're bringing into the Persian Gulf as well," said retired American general, Mark Kimmitt earlier this month.
"That is above and beyond what may be needed for the fleet.
"If it is more than Midnight Hammer I would anticipate seeing a combination of Sea Launch Ballistic Missiles like Tomahawks, I would expect to see more aircraft.
"I would expect to see a significant increase in the air defence systems in the region to protect our troops, our bases, and our allies," he said.
More aircraft — like fighter jets and attack aircraft — could also be seen on airbase aprons in Jordan.
"If you want to send a very clear message to your adversary, you bring a lot of that stuff in and you hope that deterrence message that is sent to them causes them to stand down or rethink their calculations," General Kimmitt said.
Iran prepares
Iran's actions seemed to show it was preparing for the worst, despite sitting down with the US for a second round of nuclear talks.
The country appeared to have buried tunnels leading to at least one of its nuclear facilities.
Analysis by the Institute for Science and International Security (ISIS) said all the tunnels to the Isfahan nuclear complex had been buried with soil — an apparent attempt to dampen the impact of a potential air strike or make access by special forces difficult.
Satellite imagery — supplied by Vantor — confirmed some of the entrances to the vast underground complex had been sealed off.
The imagery showed the tunnels were not buried in November last year.
The analysis noted that similar preparations were undertaken before Operation Midnight Hammer.
The ISIS researchers noted parts of the complex at Kolang-Gaz La Mountain, also known as Pickaxe Mountain, were also being reinforced. The facility is near the Natanz nuclear site.
