You could file in a state court that has jurisdiction over Gojet because it operates there on a continuous basis, Denver, Chicago, St Lousi.

Gojet may try and remove it to federal court claiming it requires an interpretation of the CBA. Gojet may try and claim that the issue has to be arbitrated.

Is the union taking a position? Union members are not really supposed to be paid outside of the CBA but your union was willingly looking the other way and letting Gojet do the bonus offers without them bing in the CBA. It goes against the whole concept of collective bargaining.