Officials easily dismissed numerous reports of UFOs tracking the London sky in 1989 as a laser light show at an outdoor Tina Turner rock concert at Wembley Stadium.

But not all "flying saucer" sightings between 1986 and 1992 have been as easily explained, according to primary documents made available to the public for the first time by Britain's National Archives on Monday.

The more than 4,500-page online document is the second batch of testimonies chock-full of shimmering objects, mysterious crop circles and creatures from another dimension collected by British military and released this month. It includes first-hand accounts such as:

• Statements from police officers in West Yorkshire describing sightings of "bright lights in the night sky"
• Testimony collected from a U.S. Airforce Sabre jet pilot ordered to "shoot down a UFO" flying over eastern England during the height of the Cold War
• A letter from a person dubbed "alien-spotter extraordinaire" who reported regular alien visits since 1982

Another of the 19 files released by the British Ministry of Defence to the National Archives details a near-miss with a possible UFO and passenger jet carrying 57 people en route from Milan to London's Heathrow Airport on April 21, 1991.

Alitalia pilot Achille Zaghetti saw a flash zoom by his cockpit windshield and screeched, "Look out, look out" to his co-pilot, the archives show.

A call placed to the control centre revealed an unknown target was spotted 10 nautical miles behind the aircraft.

An investigation into the flying object debunked Zaghetti's suspicion it was a cruise missile. The Ministry of Defence also confirmed the object was neither a weather balloon nor a space rocket.

The projectile remains unexplained to this day.

David Clarke, a UFO expert who works for the archives, suspects as many as 160 UFO-related files will be made available to the public in the next three to four years.

"Whatever you believe about UFOs, or don't believe, that is a serious incident and it has to be treated as such by the Civil Aviation Authority," Clarke told the BBC.

In another strange case, the crew aboard Britannia Airways Boeing 737, spotted a "small black lozenge-shaped object" roughly 90 metres to the left of the aircraft. 

Air traffic controllers on the ground located the oddity and clocked it at 190 kilometres per hour -- even the quickest birds can only fly about 95 kilometres per hour when pressed.

An investigation into that incident could not determine what the object was.

"Now you can look at the actual primary material -- the stuff coming into the Ministry of Defence every day -- and make your own mind up," Clarke said.