Aer Lingus has entered a 10-year agreement with Emerald Airlines to run its regional service from January 2023.
The Irish flag carrier says the new franchise will support its Dublin hub strategy by providing connectivity of UK provincial airports to North America via the Irish capital.
The agreement will offer connectivity between the island of Ireland and regional airports in Britain, the Isle of Man and Jersey.
There are also options for a network expansion to more regional airports in the future.
Under the agreement, Emerald Airlines will operate ATR turboprop aircraft on regional routes with Aer Lingus branding and livery.
While over 400 staff will be required between now and when services begin.
Lynne Embleton, Aer Lingus CEO, says: "Aer Lingus's strategic intent to develop Dublin Airport as a hub between Europe and the US, to deliver greater connectivity and aviation jobs, is significantly boosted by today's announcement.
"This franchise agreement with Emerald Airlines marks a new chapter in Aer Lingus Regional services and brings choice and certainty to our customers flying between Ireland, the UK and beyond.
"We very much look forward to partnering with Emerald Airlines, and to growing and developing Aer Lingus Regional over the coming years."
Chief executive of Emerald Airlines, Conor McCarthy, adds: "This is a major development for Irish Aviation and the wider tourism industry.
"The combined strengths of both airlines will allow us to offer optimised connectivity from popular cities and routes across Ireland, the UK and beyond.
"Emerald Airlines have ambitious plans to grow and develop this partnership over the next few years with the first ATR aircraft joining shortly.
"As we add additional aircraft to our fleet we will be recruiting 400+ new staff members which is a great boost for the industry which has been so badly impacted by the pandemic."
This announcement followed the ceasing of operations of Stobart Air back in June.
Aer Lingus will continue operating six of the former Stobart routes until at least the end of March 2022.
While British Airways is also operating four additional routes for the rest of summer period.