Ronaldo crashes Ferrari 599
The 23-year-old winger was driving the Ferrari through a tunnel on the A538, which runs beneath the airport's runways, when he crashed into a barrier.
Greater Manchester Police said Ronaldo's team-mate Edwin van der Sar was following, but that the Dutch goalkeeper was not involved in the crash.
A police spokesman said an investigation into the accident, which happened at about 10.20am, was under way.
Police also confirmed that the Portuguese international had provided a negative breath specimen at the scene.
A Manchester United spokesman said: 'He's fine and is training as normal with the team.'