NASA said Thursday it is launching a scientific study on unidentified aerial phenomena, more commonly known as UFOs, calling them of interest for both national security and air safety.

The study will start early in the fall and is expected to take about nine months to complete, according to the National Aeronautics and Space Administration. There is no evidence that the phenomena are extra-terrestrial in origin, it said.

Supplied photo shows screenshot of a video clip released by the U.S. Defense Department. (Kyodo) 

The announcement comes as attention grows over mysterious flying objects, with the U.S. Congress having held in May the first hearing on unidentified aerial phenomena in around 50 years.

Last year, the U.S. government released a preliminary assessment on UFOs, focusing on more than 140 reports collected since 2004 from military pilots and other sources. But it failed to offer concrete explanations for most of the instances.

The sole object identified with high confidence was a large, deflating balloon. The report also cited five potential explanations for UFOs, including natural atmospheric phenomena such as ice crystals as well as technologies deployed by foreign adversaries such as China and Russia.

NASA said its study, to be led by astrophysicist David Spergel, will focus on identifying available data, how best to collect future data and improving observations of unidentified aerial phenomena.

"Establishing which events are natural provides a key first step to identifying or mitigating such phenomena, which aligns with one of NASA's goals to ensure the safety of aircraft," the agency said.

The results will be shared publicly, said Daniel Evans, who will serve as the NASA official responsible for orchestrating the study.

Although unrelated to the new study, NASA said its science missions are working to find signs of life beyond Earth.