In a statement, British Air Line Pilots' Association (BALPA) said: "The issue of air transport to and from N. Ireland should not be left to the market alone and should be a matter of public policy.

"The policy should balance the sometime competing demands of consumer choice, efficiency, the best use of public investment in infrastructure and safety."

With 96% of pilots based in NI telling BALPA they are "concerned" about the future of air transport in the region, Belfast International Airport's Uel Hoey agreed airports in NI "aren't faring particularly well".

"Belfast International Airport made a 5% return on our turnover last year, Belfast City Airport on a £17m turnover registered a £15,000 profit," he explained.

The decision not to extend the runway at Belfast City Airport, which would have allowed planes to fly with heavier fuel loads and attract airlines travelling to other European destinations, was taken earlier this year.

It was welcomed by residents groups but was foreshadowed by Ryanair's departure in October 2010, when the airline blamed its decision to leave on the delays in delivering the controversial runway extension.

Mr Hoey said he believes NI needs to have a stable and thriving aviation sector to support the growing tourism sector, but he fears competition is driving business to Dublin.

"We need to get more destinations on the departure boards.

We're not actually making any progress in terms of the level of destination choice that is available and people are being forced to use Dublin as a result of that. That's bad for the Northern Ireland economy.

Uel Hoey

If the situation continues as is, Mr Hoey said an increasing number of travellers will be pushed into diverting to Dublin.

"We believe that economic value will be lost for Northern Ireland that social standards in Northern Ireland will be demeaned and, unless we adopt a strategy which will help us move forward economically and help the aviation sector to be stable and to grow, then we will lose out badly to Dublin on an economic front."

Brian Ambrose, from George Best Belfast City Airport, said if it was determined to close one of the two airports, the City Airport would most likely be the casualty.

But he said the only way to get rid of an airport, which is a private business, is to buy and shut it - an action that would take millions of pounds.

"If the decision was taken to close the City Airport, the question would be would [Belfast International Airport] behave in a monopolistic way, will they build a gateway that provides Northern Ireland with a gateway we can be proud of?

"You already have such a gateway here. A modern, bright gateway that provides a positive image for Belfast and Northern Ireland and if someone wishes to remove that gateway then they're going to have to buy it."

As the final bmibaby planes left the City Airport this week and the earlier departure of BMI, travellers have been left unsure of the security of flights leaving from Belfast.

"The need for a coherent "joined up" policy is made more urgent by the new possibility of there being no connection between N Ireland and Heathrow.

"This raises a question about economic development and how N Ireland businesses access world markets," said BALPA.

Mr Hoey added, "We have a lot of debate about competition between the airports in Northern Ireland, but in reality competition for consumers is provided by air services between airlines."