What happens on the ground when your flight diverts

Weather is the usual cause and fog is the usual weather. Heathrow and Gatwick both handle low visibility well but capacity drops sharply when they do, and an aircraft with a fuel state that will not tolerate forty minutes of holding will be sent somewhere with room. Strong crosswinds, a runway blocked by an incident, a medical emergency and a technical problem account for most of the rest.

Diversion airports are chosen for the airline, not the passenger. From a Heathrow approach the usual alternates are Gatwick, Stansted, Birmingham and Manchester; from a Gatwick approach you may end up at Heathrow, Stansted or Bournemouth. A Scottish arrival diverting from Edinburgh commonly ends at Glasgow, which is forty-five miles by the M8 and the easiest diversion in the country to fix by road.

The chauffeur stays put until there is a decision, because the single worst outcome is a car halfway up the M40 when the aircraft refuels and continues to Heathrow. Diversions that end in the aircraft continuing are common, and the flight from Birmingham to Heathrow takes twenty-five minutes. Moving the car early is the mistake an inexperienced operator makes.

Once the airline commits, the options are clear. If you are disembarking at the diversion airport, the car repositions and drives to you, which from Heathrow to Birmingham is roughly two hours up the M40. If you are being coached to the original airport, the car waits where it is, because the coach will arrive at the terminal the chauffeur is already standing in. If the flight is cancelled and you are hotelled, the car comes back tomorrow.

• The car does not move until the airline has decided
• Aircraft continuing on is the most common outcome
• A reposition from Heathrow to Birmingham is about two hours
• A coach transfer means the car waits rather than drives

This is worth saying clearly, because it goes against what a chauffeur company would prefer to sell. If the airline is running coaches from the diversion airport back to your original destination, and your onward journey starts at that destination, take the coach. It is free, it is already organised, and a car repositioning two hundred miles will not beat it by enough to matter.

The reposition is worth it in a different case: when your actual destination is closer to the diversion airport than to the original one. A passenger diverted to Manchester whose destination was Cheshire should not be coached to Heathrow and then driven back north. That is four hours of unnecessary travel, and the sensible move is to leave the airline coach and have the car meet you at Manchester.

The third case is a party with small children or somebody who is unwell. A coach at two in the morning with four hours of it ahead is a genuinely miserable proposition, and repositioning a car is worth the cost simply to avoid it. That is a judgement about people rather than mileage, and it is usually the right one.

Occasionally a UK-bound flight diverts before it reaches the UK, to Shannon, Amsterdam or Paris. At that point there is nothing a British chauffeur company can usefully do except stop charging you for a car you will not use, and help you plan the ground segment at whatever hour you eventually land.

The practical advice is not to cancel your onward arrangements immediately. Airlines will often get a diverted long-haul into its original destination the same day, and a car released at four in the morning is a car you will have to find again at eleven. Wait until the airline has confirmed a rebooking, then move the booking rather than cancelling it.