Astrid, it is the air traffic controllers who are threatening 15 minutes strike(s?). This is separate from the airport workers who are threatening day-long stikes in the run up to Christmas.
Although 15 minutes doesn't sound long, I guess it would have a major effect on travel. What would the planes do for 15 minutes? Speaking personally, I wouldn't want to be in the air for that length of time with no ATC cover. Maybe all the planes will have to land - that would certainly take longer than 15 minutes.
It all sounds like a bad time to travel in the air. Let's hope that that disputes are settled without too much disruption.
Regards
Rob