Aer Lingus (United Kingdom) (Belfast City) received its Operating Licence (OL) from the UK Civil Aviation Authority (CAA) on August 9, 2021, but has since deferred its launch from September 30 to October 20, 2021, due to the ongoing travel restrictions between the United Kingdom and the United States.

The start-up's core flights from Manchester Int'l to New York JFK and Orlando Int'l will not begin until December 1 and 11, respectively, although Aer Lingus said it remained "fully committed" to the routes. As such, its first scheduled service will be from Manchester to Bridgetown in Barbados, which remains scheduled to launch as planned on October 20, 2021.

It is the second time the airline has pushed back its launch. Originally, it hoped to begin transatlantic flights from Manchester in late July 2021. The start-up will operate services on a wet-lease basis under Aer Lingus's EI code and using its parent company's branding, with the new British carrier acting as a capacity provider to ensure compliance with the UK-US bilateral air services agreement.

The granting of the OL completes the carrier's certification drive as it had already received its Air Operator's Certificate in July 2021. Aer Lingus (UK) has already added its first aircraft, an A330-300 transferred from parent Aer Lingus, and intends to add another as well as a single A321-200NX(LR) transferred to the British AOC before it launches.

The carrier's operations are geographically restricted to the area extending roughly to Chicago O'Hare and the US Midwest and also includes the Caribbean and the northern part of South America. Destinations on the US West Coast, Mexico, or the largest airports in South America would fall outside the carrier's current permit conditions.