The strikes take places on the 8, 10, 12 y 14 of June between 10.00 and 12.00 (09.00 and 11.00 in the Canaries), and 18.00 y las 20.00 (17.00-19.00 in the Canaries). Each strike lasts two hours and the controllers will carry out 70% of their work during the strike periods.

This is the first official air traffic control strike in Spain since 1989 although the infamous wildcat strikes of 2010 caused huge disruption and even closed Spanish airspace. These mini strikes are related to the 2010 events as unions and government are still arguing over who was to blame.

Disruption to flights heading to and from the Canary IThe 2010 walkout ended when the Government used emergency powers to force the controllers back to work.slands is expected to be minimal during the mini-strikes. At worst we expect short delays as flight companies jiggle their schedules to avoid them. 

Unions have refused to rule out further similar mini-stoppages in the future if their demands aren't met.

Source: La Provincia online newspaper article (in Spanish)

More info: Air Traffic Management website