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。

youdao

As I know, if you want to refund a ticket before departure long enough, say two or three days, you will not be changed, that is to say, you can get back all your money.

据我所知，您要是在起飞前很长时间，比如说两三天，退票不收手续费，也就是说，您可以收回全额票款。

youdao

youdao

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