Everyone asks 'What can a union do for us" and not "What can we do for a union". The union is you, not a group of people in a building in a different base who you send money to each month. A union will give you advice and the backup of your fellow workers but you have to form a company council and organise yourselves. When the management see a cohesive body who have some power to affect their profits, that's when they take notice.
Leo Hairy Camel (anagram of Michael O'Leary BTW) will come on here very soon to debunk this, but it works. My company is the samller of a group of two. The largest have a very disjointed pilot body thanks to a successful campaign of splitting the workforce by the management. They now have two unions who are at each others throats and the main union has less than 50% membership. they achieve nothing and are constantly whining about the reduction in their Ts and Cs, but don't see the big picture. It reminds me of the Peoples Judean Front bitching about the Peoples Front of Judea and not bothering the Romans.
The smaller company has over 95% union membership, our Ts and Cs are intact and two years ago we got a 20% pay rise.
Divide and conquer worked for Julius Caesar and it works for airline management just as well.