IAG chief executive Willie Walsh faces a public grilling from politicians on his plans to buy Aer Lingus.
It will be the first time Mr Walsh - a former Aer Lingus chief executive - will have spoken publicly about the proposed €1.4bn takeover.
Mr Walsh will appear tomorrow afternoon before the Oireachtas Joint Committee on Transport, which is chaired by Fine Gael TD John O'Mahony.
He is expected to give more detail on how IAG would grow Aer Lingus, secure connectivity and add jobs in the future.
It marks a significant intensification of IAG's efforts to persuade both the public and political circles that IAG should be allowed to buy Aer Lingus.
But there's strident political opposition to a deal being done.
Mr O'Mahony welcomed Mr Walsh's decision to attend tomorrow's committee.
"The possible sale of the State holding in Aer Lingus is an issue of great significance to the country," said Mr O'Mahony.
Among the most prominent opponents to the takeover on the committee is Fianna Fáil TD Timmy Dooley. The Clare representative is also the party's spokesperson on transport.
Committee members including Senator Sean Barrett and Sinn Féin TD Dessie Ellis are also against the State selling its 25.1pc stake in Aer Lingus.
It is also understood that IAG, which owns British Airways and Iberia, might be prepared to offer additional concessions to the Government in a bid to win its support for an acquisition of Aer Lingus.
It has already pledged not to sell any Aer Lingus Heathrow slots without the Government's permission, and to use the slots only to serve Irish routes for at least five years following a takeover.
The appearance by Mr Walsh tomorrow will come just 24 hours after a meeting between IAG executives, including Mr Walsh, and Government advisers.
IAG top brass are due to provide even more detail this afternoon on how they would grow Aer Lingus.
Yesterday, the Dublin Airport Authority appeared to throw its weight behind a takeover of Aer Lingus.
The chairman designate of the Dublin Airport Authority, Pádraig Ó Riordáin, argued that the British Airways owner could significantly grow transatlantic traffic out of Dublin.
Mr Ó Riordáin, who has been chairman of the DAA since 2012, is in the process of being reappointed to the role by Transport Minister Paschal Donohoe.
Speaking to the Oireachtas Joint Committee on Transport, he said that while the DAA was "quite measured" on the question of an Aer Lingus takeover, IAG could be good for the airport.
He said IAG could contribute "quite significantly" in growing transatlantic traffic and developing Dublin as a hub for passengers criss-crossing the Atlantic.
"There are potential merits," he said.
"There may be some potential positives for Dublin Airport should the transaction proceed," he added.
Mr Ó Riordáin also said that Cork Airport would work to develop an expansion strategy capitalising on the IAG ownership of Aer Lingus, should a takeover go ahead.
The Transport Committee has already heard from trade and industry groups, as well as trade unions, to seek their views on a possible Aer Lingus sale.
Shares in Aer Lingus slumped as much as 10pc on Monday after reports that the Government was poised to reject the IAG takeover approach.