THE loss of Flybe services will "reduce Northern Ireland consumers' travel options to Great Britain and Europe", a consumer watchdog has said.
It comes after the airline went into administration on Saturday for the second time, leaving passengers facing disruption once again.
Flybe, which operated 10 flights to and from Belfast City Airport, had only restarted operations last April after collapsing in 2020.
A statement on the airline's website early on Saturday said it had "ceased trading" and added that it would not be able to help passengers arrange alternative flights.
Almost 140 employees worked at the Flybe base in Belfast.
Administrators have taken over the company and the UK Civil Aviation Authority said it would provide advice and information to those affected.
Matthew Hall, chief executive of Belfast City Airport, said their "thoughts are with Flybe employees and passengers affected by this disappointing and unexpected news".
Richard Williams, head of transport at the Consumer Council, said the collapse of the airline would adversely impact travel options for people in the north.
"The loss of Flybe services will reduce Northern Ireland consumers' travel options to Great Britain and Europe in the short-term," he said.
"The Consumer Council will continue to highlight the importance of regional connectivity to the Northern Ireland economy and consumers in the hope to improve consumer travel options in future."
He also urged customers impacted to be aware of their consumer rights, including compensation and assistance.
UUP assembly member Andy Allen said "passengers and employees will rightly be angry at the announcement from Flybe that the airline is ceasing to trade with immediate effect".
"An Executive, when restored, must explore the wider issue of connectivity and barriers that exist, especially around air passenger duty," he said.
Andrew Muir, Alliance MLA, said "air connectivity is so vital" for people in Northern Ireland "more so than in other areas of the UK due to lack of rail links to mainland Britain, and so this kind of loss will inevitably hit hard here".
"With that in mind, it’s essential going forward that the government works to ensure we retain that air connectivity for the routes that have been affected, whilst also prioritising the needs of the employees and passengers at this difficult time," he said.
Sinn Féin's Caoimhe Archibald has said: "My thoughts are with the Flybe workers, 138 of them based in Belfast, and their families who will be left devastated and plunged into uncertainty about what the future holds for them at what is already a difficult time with the cost-of-living crisis.
"The unexpected collapse has also caused disruption for passengers who had planned travel, and I would urge people to follow advice from the Consumer Council and Civil Aviation Authority."