A Northern Ireland consumer body has reported a near 540% year-on-year rise in complaints about airlines.
The Consumer Council said the Covid-19 pandemic had led to travel uncertainty and refund delays.
It has helped customers here get back over £250,000 in flight refunds, but it warned that many others are still waiting for their cash.
Richard Williams, its head of transport policy, said: "Throughout the Covid-19 pandemic, we have been urging the Civil Aviation Authority (CAA) to take action to ensure that airlines provide passengers refunds in a timely manner.
"On July 1 the CAA confirmed that most airlines have delayed paying refunds and we want them to enforce the law on airlines to issue refunds."
Since March 1 the Consumer Council has received over 1,300 airline enquiries and complaints, a 538% increase on the same period last year. Of these, 94% were regarding refunds. To date they have managed to get airlines to refund over £250,000 to Northern Ireland consumers.
The Consumer Council also said official travel advice had caused confusion. Last week the UK Government announced the end of the 14-day quarantine rule for travel from certain countries after July 10. This currently only applies to England. Travellers returning to Northern Ireland from outside the UK and the Republic must still self-isolate for 14 days when they get home. The UK Foreign Office has changed its travel advice for all UK travellers to now allow non-essential travel to a long list of countries.