Closing arguments get under way today in a landmark case over a secret deal between Ryanair and Northern Ireland's only publicly owned airport.
The Information Tribunal is hearing an appeal from airport owners Derry City Council against a ruling it must reveal financial details of its contract with the airline.
The disclosure order followed a Freedom of Information request, and it is believed the case could affect all UK public bodies doing business with private companies.
The three-panel tribunal - sitting for the first time in Northern Ireland - has already heard evidence from City of Derry Airport manager Seamus Devine and the council's chief executive, Anthony McGurk.
No witnesses will be called from the Information Commissioner who ordered in February of this year the contract must be released.
The final day's hearing is expected to centre on legal arguments and the exemptions claimed by Derry City Council under the Freedom of Information Act to withhold the documents.
An EU ruling in 2004 that Charleroi Airport, in Belgium, was acting illegally in providing state funding to Ryanair will also be raised.
Mr McGurk yesterday confirmed the airport was costing ratepayers in the region of £1.3 million a year, and that Derry householders pay among the highest rates in Northern Ireland.
He agreed there was considerable public debate about council spending on the airport but would not accept it would be better informed if the secret deal was disclosed.
Mr Devine said the airport would not make money for some time to come, claiming most small regional European airports are not profitable.