The US space agency was suspected of investigating the San Andreas fault, the boundary between the Pacific and North American tectonic plates that runs for 750 miles down through California.

Reports of a plane flying over the faultline emerged last month after California experienced strong earthquakes that damaged buildings and roads.

Many residents on the ground noticed the plane because it was flying below 1,000 feet.

The Los Angeles County Sheriff's Department eventually revealed that the aircraft with call sign NASA817 belongs to NASA. The DC-8 plane took off from the Palmdale Regional Airport and landed at Boise Airport, Idaho after zigzagging for more than 2,000 miles over Nevada and Central California.

NASA spokesperson Kate Squires that the plane was part of a mission called mission dubbed “FIREX-AQ” that aims to study fire smoke and air quality.

“Scientists will use data from FIREX-AQ to understand how fuel and fire conditions at the point of ignition influence the chemistry of smoke, what happens to smoke as it enters the atmosphere, and how the chemical transformation of smoke affects air quality and – to a lesser extent – weather downwind,” NASA said in a statement.

Conspiracy theorists, however, linked the plane to earthquakes, suggesting that the U.S. government could be hiding something from the public.

“With NASA817 flying over not only the San Andreas fault in California just days ago in zig zag patterns as seen in the screenshot above but also flying over dozens of potentially active volcanoes in Idaho on Wednesday as seen in the next flight pattern from Flight Aware screenshot below, do NASA and the US government know something that we don't know?” said one conspiracy site.

Representational image of earthquake that struck the area of Napa, California in the early hours of Aug 24, 2014 Josh Edelson/AFP/Getty Images

San Andreas is linked to the most catastrophic earthquake that hit California, the San Francisco earthquake of 1906 that killed 3,000 people and left half of the population homeless.

This could help explain public fear of the ‘Big One,” the mega earthquake that could cause catastrophic damages. There were also concerns that the quakes that occurred prior to the flight of the mysterious plane could potentially trigger the much feared earthquake.

Scientists said that the region is long overdue for the Big One albeit the event could happen many years from now.

“I'm certain the probability of a big San Andreas event is 100% IF YOU GIVE ME ENOUGH TIME. In other words, plate tectonics isn't stopping. But it's possible the big one is still 100 years away,” said seismologist Lucy Jones of the Seismological Laboratory of Caltech.