The strike how now been declared illegal. That isn’t likely to change things much from the strike point of view but it does give Avianca a freer hand - for example firing the strikers.
The basis for it being illegal is that the airline and the flights are critical to the national economy. There’s a fair amount of truth to that. Although the distance from say Medellin to Bogota is less than 160 miles (and therefore a half hour flight) the terrain results in it being a dozen hours by car.