The following tickets from British Airways have had their Flight change fees waived and had their validity extended until April 30, 2023:

flights scheduled after/before March 3, 2020, but before/before April 30, 2022.
tickets for flights with departure dates on or before February 28, 2021, purchased before March 3, 2020.

This means that if your travel date is on or before April 30, 2022 and you purchased your ticket on or after March 3, 2020:

Your ticket's validity has been automatically increased till April 30, 2023.
Your trip dates and destinations can be changed without incurring a fee.
You must pay the additional charge if your new ticket is more expensive.

Note

If you make changes online, British Airways won't charge you a change fee. You will be charged if you make the modifications over the phone or at the airport, though.

Free online change charge
Phone-based exchange fee: USD 25
35 USD change fee at the airport

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