Ryanair, which claims the State airport company, Aer Rianta discriminates in favour the State airline, Aer Lingus, yesterday got Supreme Court backing for its application that it is entitled to see documents in Aer Rianta's possession.

One of the three judges who held in favour of Ryanair, Mr Justice Niall Fennelly said competition cases have the special feature that any documents relating to anti-competitive behaviour are likely to be in the possession of the party engaged in that behaviour. Anti-competitive agreements or practices will be kept secret, he added.

Ryanair, which began its action in 1999, claims that at Dublin Airport it was only allocated 15 check-in desks and a half of a luggage belt while allowing 56 check-in desks and three baggage belts to Aer Lingus.

This, it is alleged was done without taking into account relative passenger numbers carried by each airline and certain spare capacity said to be enjoyed by Aer Lingus.

Aer Rianta is accused of planning a cutback to facilitate construction works in the main terminal building at Dublin Airport in 1999 so that Ryanair would lose three of its 15 check-in desks while Aer Lingus was reduced from 56 to 48.

Ryanair complain that Aer Rianta introduced a fuel levy at Dublin and provided no service in return; also introduced a compulsory service which was of value only to airlines using a computer ticketing system but of no value to Ryanair which had its own system.

The airline alleges that Aer Rianta discriminated in favour of Aer Lingus by facilitating Aer Lingus's building and operation of its own hangars while refusing like facilities to Ryanair.

The airline also complains that it was deprived of a discount previously enjoyed for the use of Pier A at Dublin which is low-cost, inferior and less convenient.

Aer Rianta appealed to the Supreme Court against a High Court order requiring it to answer all Ryanair's requirements for discovery of documents.

The Supreme Court yesterday varied the High Court order by stipulating the documents that Aer Rianta should produce and the court dismissed the Aer Rianta appeal.

Aer Rianta's claim that Ryanair did not require documentation because the airline had alternative means of establishing the relevant facts was described by Mr Justice Fennelly as a claim that had rarely been made.

Mr Justice McCracken in a separate judgment said that he considered that Ryanair had clearly identified categories of documents in relation to precise and specific allegations of abuse against Aer Lingus.

Ms Justice Denham also found in favour of Ryanair.

Ryanair was ordered by the British advertising watchdog to change claims about one of its destinations yesterday.

It follows an advert promoting cheap flights to France which included the name Lyon in small letters under the airport destination of St Etienne.

A member of the public whose daughter booked a Ryanair flight from St Etienne went to Lyon airport instead and was stranded there overnight.

They contacted the Advertising Standards Authority (ASA) complaining the wording in the advert was "misleading".

Ryanair claimed the wording was not unusual and gave other examples such as "Champagne" in small print beneath "Reims" and "Brittany" under "Dinard".

The ASA said Champagne and Brittany were regions of France in which Reims and Dinard were located, whereas Lyon was city near St Etienne.

It also pointed out that St Etienne airport was not listed as serving Lyon by the International Air Transport Users Council.

In its adjudication, the watchdog said "to class St Etienne as serving Lyon was misleading." It told Ryanair to remove the word "Lyon" from future adverts.