This has nothing to do with a strike for once !
There was some issue at Orly today with air traffic control, and the aviation authority had to cancel about 130 flights so there were fewer flights and more time in between.
They have already pre-emptively directed companies at Orly to cancel 15% of flights tomorrow, Monday, May 19th because they still don't have the problem resolved.
I am sure if you have a flight tomorrow and are affected, your airline has reached out - but you might check to be sure !!