The US Air Force has notified Congress that it will close down its High Frequency Active Auroral Research Program (HAARP), a controversial government project that conspiracy theorists believe to be responsible for everything from the disappearance of Flight MH370 to the 2011 Japan earthquake.

See related What happened to the Malaysia Airlines Flight 370

The program's main facility in Alaska was set up to study the ionosphere, a region of the upper atmosphere, with the aim of developing better radio communications technology. But since its inception in 1993, the program has been blamed for some of the world's biggest natural and industrial disasters, including the Haiti earthquake and the Space Shuttle Columbia disaster.

As the multi-billion dollar facility begins to wind down, theories about HAARP's true purpose persist. Here are some of the best (and most unusual):

HAARP caused flight MH370 to crash

Bringing together two favourite subjects of conspiracy theorists, some have suggested that the atmospheric research facility could have caused the Malaysian Airlines flight MH370 to crash. "Could HAARP be an explanation for the puzzlement that surrounds the mystery of what has happened to the plane?" asks one contributor to Godlike Productions – a self-described "conspiracy theorists and lunatic fringe" website. The plane may have gone off course because "HAARP was affecting radar systems". Pouring scorn on the theory, another reader counters: "it didn't crash so your theory is BS".

HAARP caused the 2011 Japan earthquake

Data released by Nasa shows "some strange atmospheric anomalies" over Japan just days before the massive earthquake struck in 2011, Natural News reports. The "seemingly inexplicable" rapid heating of the ionosphere directly above the epicentre of the earthquake indicates HAARP may have been responsible for the quake, the resulting tsunami, and ultimately the Fukushima nuclear plant disaster.

To further support their claim, Natural News points to a quote from the US secretary of defence, William Cohen who said in 1997 that some scientists "are engaging in an eco-type terrorism whereby they can alter the climate, set off earthquakes, volcanoes remotely through the use of electromagnetic waves".

HAARP caused the polar vortex

The east coast of the United States was plunged into freezing temperatures last year when a "polar vortex" caused temperatures to fall to unprecedented levels. Before It's News published a graphic showing "America under HAARP attack". The Freedom Agenda suspects the same cause, claiming that "weather modification" is well within the powers of HAARP, which can "manipulate the ionosphere and thereby alter the strength and the trajectory of the polar jet stream".

HAARP brought down the Space Shuttle Columbia

One of the most prominent theories about the controversial program links HAARP to the loss of the Space Shuttle Columbia in February 2003. "Columbia was used as a kind of 'target practice' for the HAARP project" suggests Mysterious Universe. It is not clear why the US would have targeted one of its own spacecraft, but according to Mysterious Universe, Marshall Smith, an ex-Nasa engineer, believes it was "a terrorist act performed by Al-Qaeda, through a graduate student with an F1 student visa".

HAARP is behind everything

"Name a natural phenomenon, and someone probably suspects HAARP of being behind it," says Stephanie Pappas, a senior writer for Live Science. Some suggest that HAARP "controls people's minds or is capable of altering the very fabric of reality", Pappas notes.

Before the official HAARP website closed down in 2013, the site’s spokespeople said that no secret research was ever conducted at the base. “HAARP is not classified," the website said. "There are no classified documents pertaining to HAARP”.

Science writer David Naiditch says it is easy to explain why HAARP is an attractive target for conspiracy theorists. It is because its "purpose seems deeply mysterious to the scientifically uninformed".

Creative commons image by Saket Vora