Not necessarily, ask Kendall CRJ pilots about how seniority works. Although the situations would be different it shows courts don’t always follow strict seniority in IR law.
You don't have to go that far back. Virgin 777 and A330 pilots had seniority and the only thing that gets them is the chance to be rehired in 2 years if Virgin are recruiting. Seniority works when the situation is normal. It is a long way from being that now and for a few years to come.