A review is to be conducted by Aer Lingus after pictures emerged of an almost full flight with no apparent evidence of social distancing measures.
The airline said any process changes required would be implemented as a “matter of urgency”.
The move came as images were shared from inside the cabin of a Belfast City-Heathrow flight on Monday morning, showing rows of seats filled with passengers.
Passenger Sean Mallon told BBC Radio Ulster there was “no social distancing whatsoever”.
“I would say there was about 95% of the seats taken on the flight,” he said.
Passengers had queued up and boarded the aircraft in the same way as they would have done before the pandemic, he said.
“The queues were down the steps and out on to the tarmac as they were before all this happened,” he added.
Passengers were not offered hand sanitiser or told of any extra safety measures as they boarded the plane, Mallon told the BBC.
The only advice they were given was a reminder to wash their hands after landing.
Aer Lingus said in a statement issued yesterday: “In light of the unexpectedly high loads on the Belfast-London Heathrow service this morning and the level of demand for the route, Aer Lingus is reviewing its processes and procedures applicable to the operation of this service.
“The safety and security of Aer Lingus’s customers and crew is our top priority and any process changes that are identified as being required will be implemented as a matter of urgency.”