A mysterious white UFO was captured speeding through the clouds by a plane passenger as his commercial aircraft passed over Iranian airspace, Express reported.

In the 34-second footage, the circular object can be seen traveling at a steady pace through heavy clouds somewhere over the center of the West Asian country. As it moves across the sky, the UFO appears to grow fuzzy around the edges before disappearing out of shot.

Since the mystery object doesn't have any wings, it echoes the classic designs of UFO's filmed in the past, with no signs of any lights, trails, or man-made machinery visible. But it could also be a drone, possibly operated by the Iranian military, according to some conspiracy theorists.

However the clip, which has gone viral, has led to speculation that it might be an extraterrestrial craft, UK MailOnline reported.

"Looks like a UFO to me, cause I don't know what it is..," online commenter Fred Smith wrote.

"I don't think this is a reflection in the window and it doesn't look like a plane so we may never know what it was. I would call it a UFO," Barney Pritchard agreed.

Witnessed and filmed by a passenger on board of a commercial airliner, the footage shows a large white object flying several hundred feet below the aircraft, moving steadily through the clouds from right to left.

Despite speculation that the object may be an alien craft, the most likely explanation is that it is high tech drone being operated by the Iranian military since the country carried out its first test flight of a drone aircraft earlier this week.

"We promised that a model of RQ-170 would fly in the second half of the year, and this has happened. A film of the flight will be released soon," Brigadier General Amir Ali Hajizadeh told the state-run IRNA agency.

Ayatollah Ali Khamenei also expressed content at the test flight, describing it as "sweet and unforgettable" in a video published by the semi-official Tasnim news agency.

As of yet, no government or organization has come forward to claim responsibility of the mysterious UFO.