A veteran and highly respected Boeing 747 captain has told The Sun Online that he has seen a number of UFOs.

Captain Christiaan van Heijst, a regular contributor to this website, told The Sun he has witnessed objects which appear to exceed all known technology as they appeared to hit hypersonic speeds of up to 23,000mph.

The 39-year-old, from The Netherlands, is a respected airman and an award-winning aerial photographer - and yet he has seen things he cannot explain.

With former US military pilots coming forward to tell about their own unexplained experiences, that piqued the interest of Christiaan.

"I realized that what they described sounded very much like some of the strange things I have seen years before," the pilot told The Sun Online.

"I always thought it was some 'military stuff' I had seen, but now it was possibly something else entirely that even stunned some of the best US military pilots on record."

Christiaan (below) has been flying for 20 years - starting out as a champion aerobatics pilot before moving over to commercial planes.

He has close to 9,500 total flight hours, 6,000 of them on the Boeing 747.

Christiaan told the Sun that while some 99 per cent of the weird stuff he sees in the sky can be dismissed, there are still a "handful" of sightings which for him defy explanation.

Christiaan emphasised to the Sun that as a pilot, he is trained to spot things in the sky - with his main objective when he's at the control being to keep his plane safe.

"If I see something that catches my eye, I immediately want to know if it is another aeroplane, something weather-related, military or anything else that might jeopardise my flight. Anything else is secondary," he told The Sun Online.

"That is also why airline pilots are credible 'trained observers': we don't search for UAP, we evaluate everything we see based on our thorough knowledge of aerial observations, and meteorological experience and wonder if anything has a direct influence on our flightpath or aeroplane."

And for Christiaan, one of his most compelling and strange sightings was over Greece as he was flying near the USS Theodore Roosevelt aircraft carrier and her strike group.

He was flying a Fokker 50 at the time and witnessed a bright light appear at an extremely high altitude - moving at an approximate speed of up to Mach 30 (23,000mph).

"No known physics can describe what that light/thing did, for as far as I know. It left no trail or anything like it, just instant speed and poof… gone," said Christiaan.

Christiaan also shared with The Sun Online what appears to be a cigar-shaped object (top photo) that he took in January 2010 - with his encounter with the object lasting over an hour.

He was flying from Amsterdam to Malaga at 41,000 feet when they spotted the shape around 100 nautical miles ahead of them.

Air traffic control told them there were no other aircraft in the area.

The object appeared to be large and stationary, hanging in the sky and blocking out part of the sun.

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