If you want to refund a ticket before departure long enough, say 15 days, you will not be charged. That is to say, you can get a full refund.

如果你在出发前较长时间，比如15天，办理退票的话，是不会被收退票费的。也就是说，你能获得全额退票。

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If the delay is for five hours or more, passengers are also entitled to a refund of their ticket with a free flight back to the initial point of departure if this is relevant (for example, if a connecting flight has been cancelled).

BBC: NEWS | Business | Q&A: Grounded BA passengers

Ticket buyers would have the right to a refund within 48 hours of purchasing a ticket, even "nonrefundable" ones.

FORBES: Fact and Comment

If you paid for tickets on or before July 22, 2011, for travel beginning on or after July 23, 2011, you may be entitled to a refund of ticket taxes already paid.

FORBES: Five Things You Need To Know About the Current Airline Ticket Tax Controversy