Pilots will work for free. I've seen an example where a couple of dudes went to the company and offered to fly a bigger type for the same money they're on to defeat the seniority system.
I've also seen a collection of guys stab a whole heap of others in the back, given up lots of conditions for a modest pay rise and promotion to another type ahead of their ex-mates.
One guy contacted the airline I work for and said his son would work for allowances only, no pay.
Airlines know pilots are suckers in general and not hard-nosed wharfies and will use divide-and-rule tactics to get what they want.