I think the problem is Americans. Americans are more interested in the O Irish situation rather than Northern Ireland. So they’re going to fly into and out of Dublin. .
What we had a few years ago with United is the best we can hope for, with another legacy airline (on the 737 Max).
Belfast needs to be made attractive to fly out of.
1. Extend the Dual Carriageway down from Antrim to the airport. Nothing is as bad as driving on a single track road through a council estate to get to the airport.
2. Add buses to areas other than Belfast.
3. Open a train station, with routes to Belfast and Derry/Londonderry, Coleraine, Ballymena, Bangor etc.
4. Upgrade the whole airport. Expand the passenger terminal, including the security and the eateries, bring in more than one jet bridge. Belfast’s terminal is well past it’s sell by date.