If your flight is cancelled
The airline must offer a refund or another flight, plus care while you wait: meals and, if needed, a hotel. This applies whatever the cause.
Compensation of €250 to €600 is separate and depends on the reason. A strike by the airline's own staff over labour demands does not, in principle, exempt it from paying (CJEU, C-28/20). The same judgment accepts that it may exempt the airline if the strike stems from demands only the public authorities can satisfy, which may matter in a general strike. A strike by outside staff, such as airport or air traffic control workers, may also be an extraordinary circumstance. In every case the airline has to prove it, and it has to be checked case by case.
If your train is cancelled
We have not yet seen Renfe's terms for that day. When they are published, check the change or refund options for your ticket. If the train runs late, see the refund table.
What to keep
Keep your boarding pass or ticket, the cancellation notice, and receipts for meals, hotel and transport. Claiming is much harder without them.