According to the Live Flight Information site TUI flights to Reus (in Spain) and Palma de Mallorca (in Spain) have been delayed.
When asked for a comment a spokesman for TUI (in statements on Dalaman and also Palma) said the Palma flight has been rescheduled for this afternoon.
"We’d like to apologise to customers travelling on flight TOM816 from Belfast to Dalaman which was unable to depart as planned on Monday 21 May due to operational issues.
"All impacted customers were offered overnight accommodation while we worked through a new flight plan.
"Customers then departed for Dalaman at 09:00 today BST and the flight had to make a short stop in Chareleroi due to knock-on effects of the delay.
"Customers on this flight are entitled to compensation in line with regulations and we have proactively sent them information on how to submit a claim.
"We appreciate our customers’ patience and understanding and we are sorry for any inconvenience caused."
It is understood the airline needed to pick up more crew in order to be able to continue the flight as the overnight delay causing disruption to staffing rosters.
Meanwhile in another statement, a spokesman for TUI said: "We’d like to apologise to customers travelling on flight TOM1242 from Belfast to Palma which was delayed due to operational issues.
"We have offered food and drink vouchers to all affected customers and have been in regular contact with them, advising them of their new departure time as soon as we could.
"We understand that delays are frustrating, we appreciate our customers’ patience and we are sorry for any inconvenience caused."
Also according to the site Easyjet flights to the airport have arrived or are not expected to be delayed.
Easyjet have also been asked for a comment on the issue.
It has been reported on UTV that a number of TUI flights have been disrupted from Belfast International since the weekend with holidaymakers jetting off to the likes of Kos, Malaga and Dalaman also facing severe disruption.
Over the weekend a number of EasyJet flights to the likes of Faro, Gatwick, Liverpool and Bristol were also disrupted'.