I dont agree with the previous person. For sure acts of God, some are not covered. But I have worked in insurance and it depends on what has happened and to what.
I have found the following info: You dont say whether it is a package or they booked flights only?
What if my flight is cancelled?
According to EU regulations, if your flight is cancelled within seven days of departure, you are entitled to a full refund.
A refund is payable within seven days of the departure date, according to the Air Transport User's Council, and applies to any parts of the tickets not used.
If you agree to be re-routed, either as soon as possible or at a later date, the airline must reimburse the cost of a transfer if it doesn't transport you to your original destination.
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What if it was a connecting flight?
The AUC offers this advice to transfer passengers: "If it is a connecting flight and you have already made part of the journey and do not want to continue with it, reimbursement of the total price of the ticket (including parts of the journey not made if the flight is no longer serving any purpose in relation to your original travel plan) within seven days and a free flight back to point of departure."
What about the cost of extra hotel nights or forfited hotel and car rental bookings?
You are not entitled, under EU regulations, to reimbursement of any other components of your trip such as hotel and transfer costs, says the AUC.
What if it was a package holiday?
If you have bought an ATOL-protected holiday from a
travel agent, the agent will take responsibility for rebooking an alternative holiday if your flight is cancelled. Alternatively, if you are stranded abroad, the agent or relevant tour operator will organise alternative flights or hotel accommodation.
Do I get any compensation for the incovenience?
The airline is not entitled to pay compensation if it was caused by circumstances that are beyond its control, which includes adverse weather.
What about costs incurred while my flight is delayed?
The regulations are not clear cut in this area, with assistance depending on the length of delay and length of the flight. Passengers should be given meals and refreshments, two free telephone calls, emails or faxes and overnight hotel accommodation and transfers where appropriate. The full details are listed on the AUC website.