Ministers have admitted they would be powerless to prevent British Airways from cutting its links with Northern Ireland.
Fears have been raised that the carrier would axe short-haul links between London Heathrow and Belfast in favour of more profitable international destinations.
Yesterday Transport Minister Theresa Villiers revealed talks were under way with the European Commission on whether landing slots could be "ring fenced" for strategically important domestic services. But she said this would be difficult to achieve.
And on the future of BA services to Heathrow, she told MPs: "We can't direct them (BA) -this is a matter for them."
There are "almost no levers that the Government has on this kind of issue", she added.
The Conservative minister was giving evidence to the Northern Ireland Affairs Select Committee, which is investigating the future of the province's air links.
She said Northern Ireland's domestic links were "absolutely essential" for the economy. BA has "no plans" to stop the flights, she said, saying: "My understanding is that it's the commercially attractive option."
But the long-term situation was another matter, she said.
David Simpson, DUP MP for Upper Bann, told her: "BA walked away from Northern Ireland in 2001. Despite assurances that Willie Walsh is giving, there is still that doubt, lack of trust, call it what you want, that in the not too distant future BA will pull out of Belfast."
Although the Government will explore ring-fencing landing slots, Ms Villiers said it would not be backing former Ulster Unionist leader Lord Empey's bid to change the law.
Lord Empey has launched a private member's bill which would give the Government the power to require airlines to maintain domestic links.
The minister said she understood the sentiments of the bill, but added: "I'm afraid we are not able to support it. What it asks the Government to do is not permitted under current EU law."
The minister also hit back at calls for Belfast to be served by just one airport. Last week the pilots' union said it did not "make sense" to have the city and international airports competing for business.
She said the Government could never ask an airport, as a private business, to close, adding: "We believe there are real benefits to passengers of having two airports."
Earlier, Northern Ireland's air links were highlighted during Prime Minister's Questions by the DUP's William McCrea.
The South Antrim MP raised fears about services between Belfast International airport and Heathrow. Standing in for David Cameron, who is overseas, Foreign Secretary William Hague said Belfast's links with London were important, and pointed to the Government's decision to devolve the setting of air passenger duty to Stormont.