The planned strikes will take place on 8th, 10th, 12th and 14th June. They are planned to take place between 10:00 and 12:00 and then again each of the days from 18:00 to 20:00.
At the moment it is difficult to say how this will affect flights, but some airlines will change their schedules so check with your airline before you travel. The Canary Islands are often not affxected directly as aircraft flying here do not always go over mainland Spain, if flying from the UK. However, these may be affected by knock on delays from other inbound flights.
More on this as we get nearer to the 8th June.