NASA's UFO team has held its first public meeting. Here’s what we learned from its experts

NASA held its first public meeting on UFOs on Wednesday, a year after launching a study to unravel the unexplained sightings that have long fascinated the general public.

The space agency televised the four-hour hearing featuring an independent panel of experts who vowed to be transparent. The team was made up of 16 scientists and other experts selected by NASA, including retired astronaut Scott Kelly, the first American to spend nearly a year in space.

The studies seek to probe what NASA calls UAP- short for unexplained anomalous phenomena - in the sky, in space or under the sea.

The subject is a very serious one, the US space agency stressed, as it concerns both national security and air traffic safety.

Still, hundreds of questions from the public that poured in ahead of time were skeptical and veered into conspiracy theories.

“I want to emphasise this loud and proud: There is absolutely no convincing evidence for extraterrestrial life associated with” unidentified objects, NASA's Dan Evans said after the meeting.

Optical illusions can explain some of these, said Kelly. He recalled an episode years ago at Virginia Beach - on the east coast of the United States - during which his radar intercept officer in the back seat was convinced they’d flown past a UFO.

“It turns out it was Bart Simpson, a balloon,” he said. “And in my experience, the sensors kind of have the same issues as the people’s eyeballs”.

Some 800 unidentified aerial phenomena have been collected, Sean Kirkpatrick, director of the All-domain Anomaly Resolution Office, said on Wednesday. But "maybe only between 2 per cent and 5 per cent" are "really abnormal,” he said.

During the meeting - held at NASA’s headquarters in Washington with the public taking part