Well in the UK, we don't have a "Union".
It's an association and has less teeth than an 80 year old life time coca cola drinking and no stomach for a battle.
If your thinking Union, you need to think RMT.
Anything else and you may as well tear up your 1% and throw it to the wind if your outside maybe 3 major major airlines in the UK.
When was the last UK pilot strike?