Originally Posted by KARFA

There are two options here:

1. rebook as a result of a cancelled flight, in which case you can book regardless of reward availability on the same route, but it must be within ticket validity (1 year from when originally booked)

2. take a future travel voucher (flights don't need to be cancelled for this) which holds your cash, avios, and voucher which expires April 2022. You can book up to the expiry of April 2022 but you will need reward availability.