Shannon Airport hopes that the Aer Lingus deal will herald a "new era" for both the airline and the region.
Shannon Group chairman Rose Hynes welcomed the IAG takeover of Aer Lingus and the Government decision to sell its shareholding in Aer Lingus.
"An IAG takeover of Aer Lingus opens a new era, not just for Aer Lingus but also for Shannon Airport and the region.
"It's good news; it's a positive opportunity for Ireland, will safeguard the Shannon Heathrow connectivity for seven years and it opens the door to further growth at Shannon," she said.
But former Shannon Airport Authority director Tadhg Kearney warned the Coalition that "the devil will be in the detail".
He said that guarantees would be broadly welcomed over the Heathrow slots.
"These are issues of absolute critical importance for the mid-west region, in particular."
But Mr Kearney added that it was an issue of deep concern that British Airways (BA) has concentrated its transatlantic services from London airports - with other carriers focusing on long-haul services from regional airports such as Manchester and Birmingham.
"Are BA going to maintain two transatlantic hubs in Ireland after any Aer Lingus deal?" he asked.
Both the south-west and mid-west regions have been worried about any threat to Heathrow routes operated from Shannon and Cork.
The prized Heathrow slots controlled by Aer Lingus are worth as much as €400m - and there are fears these could be transferred from short-haul Irish/UK routes onto more profitable long-haul routes operated from London.
Lord Mayor of Cork, Councillor Mary Shields said the south-west depended on the four daily Heathrow departures.
She bluntly warned that the Heathrow slot guarantees were absolutely critical as the deal moved ahead.
Aer Lingus axed its Shannon-Heathrow services in 2007 before reinstating the routes under intense pressure two years later.
Limerick Chamber of Commerce also stressed that current transatlantic services were vital to maintaining Shannon's prized US immigration pre-clearance status.
Cork Airport, which has no transatlantic routes, has four daily Aer Lingus departures to Heathrow and the route is the most heavily booked and profitable at the facility.
The services are operated by Aer Lingus on a code-share basis with BA.
Both Cork Chamber and Cork Business Association said there was no reason why IAG should not be encouraged to invest in new routes from Cork and other Irish airports.