Hundreds of flights were cancelled on Monday after the UK's air traffic control systems were hit by a major technical fault - with thousands of passengers stranded.
And amid concerns that disruption could last well into this week, Britons stuck abroad - and those planning to travel in the coming days - will want to know what their rights are.
There's good news and bad news. While you're entitled to some support, airlines do not have to provide compensation for delays and cancellations because these technical faults are classified as "extraordinary circumstances".
Airlines do have an obligation to keep passengers comfortable in the event of a "significant delay" - with the Civil Aviation Authority setting out a clear definition of what meets this threshold.
You'll qualify for support if a short-haul flight under 932 miles (1,500km) is pushed back by two hours. This rises to three hours for journeys up to 2,175 miles (3,500km).
For long-haul flights going any further than this, four hours or longer counts as a significant delay.
This applies to all passengers flying from a UK airport, returning to the country on a British or European airline, or arriving in the EU on a UK carrier.
What am I entitled to?
In the event of a significant delay, airlines must give passengers:
• A reasonable amount of food and drink
• Refunds for the cost of two free phone calls, faxes or emails
• Accommodation for passengers stranded overnight
• Transport to a hotel - or their home
Of course, when there are hundreds of passengers who need assistance, airlines may be unable to organise this support in a timely manner.
Because of this, the Civil Aviation Authority says affected consumers have the right to make their own "reasonable" arrangements - but they must keep receipts in order to be reimbursed.
"Reasonable" is a key word here, and you might not receive full compensation if you book a five-star hotel or have alcohol with your meals.
Will I get compensation?
This is where the bad news kicks in.
Usually, airlines do have to provide compensation if their flights arrive three hours late - but air traffic control problems don't count because these technical issues aren't their fault.
And if you agree to travel on a later flight, the airline is no longer obliged to offer food, drink or accommodation while you wait.
Thankfully, you are entitled to a full refund if you decide to abandon your journey after five hours of delays.
What if I'm about to travel?
Transfer passengers who end up missing a connecting flight because their first plane was delayed are entitled to a service back to their original departure point.
But things get a little more complicated for passengers on package holidays - especially if they decide not to travel on a delayed outbound flight.
The CAA's guidance says: "You may lose your holiday too, so we recommend you contact your package organiser or the airline for further information.
"If you still want to travel then your airline must get you to your destination. You might have to be patient while they rearrange transport and rebook passengers, but the law says they must get you there."
Many travellers end up booking their flights, hotels and excursions separately - and if you're unable to cancel your accommodation or activities, you may be able to claim back on your travel insurance if it's a comprehensive policy.