National Express is withdrawing all 12 of its double-decker coaches as a precaution after two people died in a crash near Heathrow Airport.
A number of people were seriously injured when the London to Aberdeen service overturned on an M4 slip road.
The coach's 40-year-old driver has been arrested on suspicion of causing death by dangerous driving.
The double-decker coaches will be taken off the road when they have reached their destinations.
National Express said the firm wanted to carry out inspections of the vehicles given the seriousness of Wednesday's crash.
The company said there was no suggestion of any stability problem with the coaches at this stage.
Paul Bunting, National Express chief executive, said: "As a precautionary measure, we felt it necessary to temporarily withdraw the fleet as soon as possible.
"We will ensure this process is thorough and comprehensive as part of our commitment to passenger safety."
He said it was a sad day for everybody at National Express and thoughts and condolences were with the families of the dead and the injured.
Police have confirmed no other vehicle was involved. The coach driver is being interviewed in Berkshire after being arrested by Thames Valley Police earlier.
The 69 people on the coach, which included children, were taken to hospital following the crash.
The woman who died was later named as Chris Toner, 76, from Monifieth, near Dundee.
Doctors said the other fatality in the accident, which happened on a slip road from the M4 to the M25, was a man in his late 20s.
Thirty-six passengers, including those fatally injured, were taken to Hillingdon Hospital, in west London.
Trauma consultant David Houlihan-Burne said many of the patients came in with their wounds contaminated by mud and grass.
He said medical staff had a well drilled emergency plan as they were so close to Heathrow airport.
Other casualties have been taken to various London hospitals and one in Slough suffering from a range of injuries.
James Lant, told the BBC how his stepbrother, 69-year-old Michael Milbourne, was returning to Scotland after spending Christmas and New Year with his family in London.
He said Mr Milbourne suffered a fractured vertebra and a cut to his head.
He said his stepbrother told him how the coach was going on to the slip road on the M25 when it veered to the left then right and then went out of control.
"He was in a bad way. There were people distressed all around him and inside the coach people were on top of one another," said Mr Lant.
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"He was trying to help people but he couldn't really move because of his back."
The coach was a number 592 service, which left London Victoria at 2230 GMT and was due in Aberdeen at 1030 GMT.
As well as the 67 passengers, there were two drivers on board the service, which was due to stop at Heathrow Airport, Carlisle, Hamilton, Glasgow and Dundee.
National Express said most of the passengers were going to Glasgow.
Among them were people returning from holiday and some foreign nationals.
The coach has been moved to a garage in Oxfordshire where it will be examined by accident investigators.
Inquiries surrounding the circumstances of the crash are continuing.
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