There is a general strike in Spain today that will also affect public transportation and airlines operating to/from/within the country.
Some flights are guaranteed, but looking at the status at various flights, it seems that there are significant cancellations, and both passengers and employees may have find it challenging to get to the airports.
European Union Air Passenger Rights EC 261/2004
A general strike is outside airlines’ control, so they are not, by default, liable for delay compensation if a passenger arrives at their destination late.
Airlines are, however, required to provide Duty to Care and rebook affected passengers to their final destination at the earliest convenience.
Duty to Care includes accommodation and meals in case of long delays.
Airlines are required to rebook passengers with canceled flights to their final destination, even on other airlines.
Note that this applies to Community Carriers (airlines based in EU/EEA), and flights on all airlines from EU/EEA.
Conclusion
This should be a one-day strike only andthe target is not the airlines, but the cost of living expenses and wages that haven’t kept up with inflation.
But passengers are also caught with this, which is unfortunate.