The Labour Court hearing involving Ryanair management and the pilots' union IMPACT has been adjourned until Monday at 2pm.
It is understood that during the three and a half hour hearing, both sides made detailed submissions but it was felt that the court would need more time to consider the issues.
Ryanair has never recognised unions, arguing that it prefers to deal directly with staff.
But the Industrial Relations Act of 2001 allows unions to complain to the Labour Court if an employer will not negotiate with them.
Crucially, even if the employer ignores the proceedings, the Labour Court can issue a binding recommendation which is legally enforceable in the Circuit Court.
Ryanair chief executive Michael O'Leary argues that the legislation introduces compulsory union recognition by the back door and has threatened to mount a constitutional challenge to the legislation.
At today's preliminary hearing his legal representatives were expected to argue that the legislation was never intended to apply to a high-pay multinational like Ryanair, with internal collective bargaining mechanisms.
Arriving for today's hearing, IMPACT assistant general secretary Michael Landers said Ryanair was entirely free to challenge the legislation but added that in the interim the union was proceeding on the basis that the act is constitutional and valid.
* Ryanair today awarded Sr Kathleen Murphy from Edinburgh with €100,000 cash prize as the airline celebrated carrying its 100 millionth passenger. Ryanair has been running a special promotion to celebrate the landmark as the first European low fares airline to carry 100 million passengers.
All passengers who booked return flights with the airline between September and November were eligible for a draw to win the cash prize. Sr Kathleen Murphy was one of over 700,000 eligible passengers who took part in the promotion throughout Europe.
