IAG boss Willie Walsh will meet Aer Lingus unions in Dublin today.
Around 20 representatives of SIPTU, Impact and ICTU will ask Mr Walsh on how new jobs would be created at the airline if IAG's takeover is successful.
It is understood Aer Lingus CEO Stephen Kavanagh will also be in attendance.
Unions are yet to be convinced by IAG's plan to takeover Aer Lingus, and today's meeting could be key to whether or not their resistance eases.
SIPTU, Impact and the Irish Congress of Trade Unions will be asking Willie Walsh for details on how IAG would affect jobs at the airline.
The unions have warned they will not give the sale their backing unless they get cast-iron guarantees about employment terms and conditions.
Willie Walsh, himself a former union rep at Aer Lingus, has previously said administration jobs would be lost - but says more jobs would be created among air crew and mechanics.
SIPTU Divisional Organiser Owen Reidy said unions remain to be convinced.
"At this moment in time, most of use would be fairly sceptical - until, or unless, we get the tangible guarantees."