Pilots at Ryanair are to lodge a pay claim today in a bid to bring their salaries into line with better-paid pilots at Aer Lingus.
The Impact trade union said it would lodge the claim with the Labour Relations Commission today.
Impact said Ryanair was likely to reject an LRC intervention and that the claim will then be referred to the Labour Court, which is currently considering an Impact claim against Ryanair under Ireland's Industrial Relations (Amendment) Act, 2004.
Ryanair refuses to negotiate with trade unions representing its staff.
Impact said it had lodged the pay claim with Ryanair management last month and that "unsurprisingly", the company rejected it.
In a statement, the union said it now believes Ryanair's bid to take over Aer Lingus "substantially strengthens the union's claim for a closer alignment of pilots' remuneration and working conditions in the two airlines".
In October last year, the High Court rejected Ryanair's claim that the Labour Court did not have jurisdiction under the 2004 Act, which allows the Labour Court to set pay and conditions in companies that don't engage in collective bargaining.
Ryanair has appealed to the Supreme Court, which is expected to make a ruling shortly.