Thick fog across the South of England has led to flights being grounded and some cancelled at Heathrow, the UK's busiest airport, and City Airport in London.
Here's our guide to your rights when flights are delayed or cancelled.
My flight is cancelled. What can I expect?
Flight compensation depends on whether or not the airline is at fault for the cancellation. In this case, you would not be entitled to compensation as the cancellations are caused by heavy fog and therefore out of the airline's control - airlines don't have to pay if there have been 'extraordinary circumstances' that were outside their control. However, you should still be offered a refund or another flight to your destination following the cancellation.
What are these extraordinary circumstances?
According to the Civil Aviation Authority, they include: bad weather; political instability; security risks; unexpected flight safety complications; strikes; and air traffic management decisions.
I thought a recent court ruling meant bad weather wasn't 'extraordinary'?
EasyJet lost a county court battle in September 2013, in a case involving a woman whose 2012 flight from Gatwick to Nice landed three hours and 12 minutes late due to bad weather. She was awarded £210 in compensation. However, EasyJet later argued this was not a landmark ruling that would open the floodgates to thousands of similar claims, because it was at county court level and therefore did not set any legal precedent.
My flight is delayed, so can I claim compensation?
Irrespective of the cause of the delays, if your wait is longer than four hours (two hours on some flights) after the original departure time, the airline must look after you. This includes: paying for your meals, drinks, accommodation if the delay is overnight, and keep you informed of what's happening with your flight. If your flight is delay more than five hours you are entitled to a refund.
I missed a connecting flight. Will I be looked after?
If flight delays or cancellations have caused you to miss a connecting flight at another airport, you should be covered by your travel insurance.
I thought an EU rule meant I could get compensation for delays or cancellation?
Under EU regulation 261/2004, passengers are entitled to compensation from the airline if a flight is cancelled or delayed - but, again, it doesn't apply to flights affected by bad weather.
If you were entitled to compensation, according to EU law, you would get:
• from €250 (£210) for a flight less than 1,500km and delayed by more than three hours
• €400 for the same delay for a flight between 1,500km and 3,500km
• €600 for delays longer than four hours for flights further than 3,500km.