Media playback is unsupported on your device Media caption Ed Thomas reports on a day of cancelled flights

Airports across the UK are returning to normal after three days of disruption due to fog.

A small number of departures were cancelled on Tuesday morning at Heathrow, London City, Belfast and Leeds Bradford.

But a Met Office "be aware" warning of dense fog until midday on Tuesday was lifted early.

Heathrow cancelled 129 flights on Monday, with problems compounded by fog in much of western Europe.

Fog was forecast for the north Midlands, northern England and southern Scotland on Tuesday morning, but the impact on travel was relatively minor.

Why does fog still disrupt flights?

Foggy UK: In pictures

Heathrow said it had cancelled 11 flights and London City eight.

Two flights were also cancelled at Belfast City, along with a small number at Leeds Bradford.

Heathrow said on Twitter: "Visibility has improved today. We still advise you consult your airline before flying."

Gatwick also tweeted: "Fog is clearing this morning, however passengers should continue to check with their airline for the status of their flight."

On the roads, Traffic Scotland warned drivers in the Falkirk, Fife and Strathclyde areas to take care in foggy conditions during the morning rush hour.

On Monday:

Image copyright Reuters Image caption Fog engulfed the towers of the oil refinery in Pembroke, Wales, on Monday

Image copyright Cyndi Pitcher Image caption BBC reader Cyndi Pitcher sent in this picture taken from the Millennium bridge in Gosport, Hampshire

Image caption An aerial photograph shows the top of the shard just visible above the blanket of fog

A family stranded in Spain were told they will have to fly back from Alicante to Southend instead of Valencia to Gatwick on Wednesday because of the fog in the UK.

Marina Norris, from Brighton, said: "We have to find our own way to Alicante and our own way back from Southend. We have absolutely no other support."

Terry Halpin told the BBC he was in a hotel near Gatwick, hoping to fly home to Dublin with his two children. He said there had been very little information or help from his airline or airport staff.

He said: "I've two kids here, I don't know this part of England and they just said, 'look, you have to look after yourself'."

Louise Baker, from Bridgend, has been stuck in Paris with her family since Sunday night.

She said: "No food, no drink, no nothing. We've been left here as if we don't exist by our company."

Why is it so foggy?

Media playback is unsupported on your device Media caption BBC Weather explains how fog forms

By Steve Cleaton, BBC Weather forecaster

The sort of fog we've been experiencing is known as radiation fog.

It tends to form most readily on clear nights with light winds - conditions that are usually associated with high pressure systems, or anticyclones.

Anticyclones initially tend to bring a good deal of settled and dry weather by day, but as the sun goes down in the evening, the air temperature steadily drops and eventually cools to a point where any moisture condenses out into fog - hence why the foggiest conditions are often found towards dawn.

There has also been very little wind to help clear it and as we're into November the sun is lower in the sky, so it's weaker as a heat source, meaning the fog has persisted all day in some areas.

Driving in fog

Motoring organisation the AA advises:

According to the Highway Code, you must use headlights when visibility is seriously reduced - generally when you cannot see for more than 100m (328ft), or the length of a football pitch

There's no obligation to use fog lights but if your car is involved in an accident and they weren't on, then your insurer may ask questions

Generally it's better to be safe than sorry, so use fog lights when appropriate, but don't keep switching them on and off - this can be a distraction to other drivers so wait for a consistent improvement in visibility before turning them off

Be able to stop within the distance you can see clearly

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