A near-miss between two planes at Barcelona's airport in Spain has been caught on camera by an aviation enthusiast.
A Boeing 767 from Russian airline Utair is shown coming into land on the runway. As it approaches the ground, an Aerolineas Argentineas Airbus A340 taxis across its path.
The Utair jet pulls up and performs a 'go-around'. The plane lands safely shortly afterwards.
The incident, caught on camera by Miguel Angel, who posted the video to YouTube, occured on Saturday. The video has since been viewed more than 1 million times.
Angel, who has posted hundreds of plane videos to his channel, most of which have only a few hundred views, said online that seeing the incident unfold before his eyes was "one of the worst experiences I have ever had".
Captain John Holmes, flight training manager at Ansett Aviation Training said there were three possible explanations for the error.
"The instructions to the A340 possibly were misunderstood by the captain, or they might not have heard or acknowledged the instructions, or there may have been no instruction issued from the control tower," he said.
Captain Holmes said normally a "hold short" instruction would be issued to the taxiing aircraft, ordering the pilots to stop the plane and not pass on to the runway.
Captain Holmes said the pilots on board the Utair plane would have had a clear view of what was happening and would have been ready with their hands on the throttle to abort the landing and perform a go-around - a very common procedure that is regularly practiced by pilots.
Meanwhile, US Federal Aviation Administration (FAA) authorities say air traffic controllers at a Houston airport narrowly averted a potential midair collision of two planes.
The incident happened on Thursday night 16 kilometres northeast of Bush Intercontinental Airport, when a Singapore Airlines 777 jumbo jet and a Delta Airlines A320 came about a half-mile (800 metres) horizontally and about 200 feet (60 metres) vertically of each other.
Federal guidelines say aircraft should be separated a half-mile (800 metres) vertically and three miles (4.8 kilometres) horizontally.
FAA's Lynn Lunsford told the Houston Chronicle that an air traffic controller noticed the danger and gave pilots instructions.
Lunsford says they have taken steps to ensure flight crews are aware of the guidelines.
In May, the FAA was investigating an incident in which an air traffic controller's mistake put two planes on a collision course.