Ryanair has begun its new services from George Best Belfast City Airport on Tuesday.
Ryanair is flying to four routes from the city
The airline will operate flights to London Stansted, Liverpool, East Midlands and Glasgow Prestwick.
Ryanair said it expected to carry up to 200,000 passengers to and from its new base every year.
It said it was basing a new Boeing 737-800 aircraft at the airport and was committed to widening its route portfolio from Belfast.
Alan Clarke, Chief Executive of the Northern Ireland Tourist Board said the move was good news for tourism.
"Over recent years, we have seen huge growth in direct air access to Northern Ireland with visitor numbers from Europe rising by 19% as a result," he said.