The steady flow of military assets moving towards Europe and the Middle East appears 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.
The data from tracking website Flightradar24 shows 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 shows 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 is just some of the aircraft which have made the trip, as the data is only from flights which had tracking systems turned on.
In the last few days, plane tracking experts have 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 the last day has been one of the most active periods of movement during the last 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.
Crucially, E-3 Sentry airborne warning and control systems (AWACS) — distinctive aircrafts with radar domes perched on the plane body — began being tracked on Tuesday 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 shows 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, shows aerial refuellers, transport aircraft and a reconnaissance aircraft on the apron.
Mr Watkins said tracking the aircrafts' departure location can give clues as to what they are 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 have 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 Sunday — the first time it has been seen since its arrival in the Middle East in January.
US media has reported another aircraft carrier, USS Gerald R. Ford, is 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.
"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 — can 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 seem to show it is preparing for the worst, despite this week sitting down with the US for a second round of nuclear talks.
The country appears 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 have 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 — confirms some of the entrances to the vast underground complex have been sealed off.
The imagery shows the tunnels were not buried in November last year.
The analysis notes that similar preparations were undertaken before Operation Midnight Hammer.
The ISIS researchers note parts of the complex at Kolang-Gaz La Mountain, also known as Pickaxe Mountain, are also being reinforced. The facility is near the Natanz nuclear site.
