A bit off topic, but for what it's worth if anyone wants to read the "struck work letter" from ALPA and the resolution from the Spirit MEC, here it is:
struck work letter
I hope the link works. Interestingly, the MEC does NOT consider it struck work for another carrier to fly on Spirit's routes and frequencies for their own benefit, as long as it does not benefit Spirit management in the form of flying Spirit airplanes or a wet lease. In fact they are encouraging it. I guess it puts additional pressure on their management since it could mean permanently lost business. It's also good PR for the Spirit pilots since they are trying to take care of their passengers by asking others to fly their routes.
Personally I've never seen such a thing. I always thought struck work is off limits and would not fly "extra sections" to poach flying from a striking airline. But in this case the pilots are actually encouraging it.