Cut on air duty kept operation in Belfast
The Belfast-Newark route was initially threatened because air passenger duty on transatlantic routes was 20 times higher in the UK than the Irish Republic.
When the route opened in 2005 it was profitable, but rises in air passenger duty in the UK and falls in the Republic undermined the business model.
The Belfast Telegraph revealed there were fears Northern Ireland could lose its direct flight to New York in 2011.
There were concerns it would be axed as part of a merger deal involving Continental Airlines, which operated the loss-making route.
In November of the same year the air passenger duty (APD) for direct long-haul routes from Northern Ireland airports was cut.
APD is an excise duty which is charged on the carriage of passengers from a UK airport.
Rates fell to £12 per passenger in economy and £24 for business and first class passengers.
The move guaranteed the continued operation of the Continental Flight from Belfast International to New York/Newark which was under competition from Dublin.
The old rates added £60 to an economy fare and £120 to a business ticket.
Continental said it had been absorbing the cost in Belfast in order to avoid passengers simply opting for Dublin.
APD on long-haul flights is a devolved matter and Stormont had already abolished air passenger duty in this regard.
At the time Northern Ireland Finance Minister Simon Hamilton had said it would be too expensive for Stormont to take steps to entirely devolve APD.
A spokeswoman for Belfast International Airport – where United Airlines operates our only international air route from Belfast to Newark/New York – said: "Any tax which makes our gateways less attractive than those across the border is retrograde."