It comes as Aer Lingus has cancelled more than 60 flights over the past week.
Yesterday 25 flights which were due to depart and arrive at Dublin Airport across Friday and Saturday were grounded, leaving hundreds of passengers stranded.
Among them, industrial action at Lyon airport has led to the cancellation of two return flights to its airport today.
Flights to and from Gatwick and Amsterdam have also already been cancelled.
It comes as figures show those worst hit by the summer wave are people of working age from 25 to 54 although the true level of infection is unknown.
The positivity rate for people having HSE PCR tests rose to over 40pc yesterday, the highest in months and the number of patients in hospital with Covid-19 rose to 812, with 32 in intensive care.
UCD virologist Professor Gerald Barry said Covid-19 vaccines should not be allowed go out of date. “Open them up,” he urged, to allow people who would like a second booster shot but are currently excluded from getting the top-up jab.
It comes amid growing concern that a spike in Covid cases will affect transport services across the country as the peak summer holiday period gets in full swing.
Although key transport operators, including Bus Éireann, Dublin Bus and Irish Rail, say disruption has been kept to a minimum so far, all are acutely aware of rising Covid levels among workers.
The National Transport Authority of Ireland (NTA) said all public transport operators are currently facing a growing challenge in the recruitment and retention of staff, and that some services are having to be cancelled at short notice due to Covid and other illnesses.
Bus Éireann said in the past three weeks it is seeing an increase in Covid-19 cases among its staff, and several services have had to be cancelled.
A spokesperson for the bus network said that currently, nationwide more than 98pc of services are operating in line with the scheduled timetable.
Irish Rail currently has 38 employees off due to Covid-19, which it says is less than 1pc of its staff overall, and this currently isn’t having an impact on services.
Dublin Bus is seeing around a 2pc staff absence with around 50 drivers currently off due to Covid-19, a transport union representative has said.
Earlier this week, the NTA said it could not put on more services for concerts in Marlay Park, Dublin, due to a lack of staff.
“In general services are quieter over the summer months as schools and third-level colleges are closed,” a spokesperson for the NTA said.
“The authority welcomes the additional passengers from the different events happening over the summer but in many cases does not have the capacity to put on additional services for those events, particularly if they impact on the operation of regularly scheduled services.”
General secretary for the National Bus and Rail Union (NBRU) Dermot O’Leary said that although transport operators are only experiencing a 1pc to 2pc shortage of staff, this “would have an impact”. “I do understand that there are several operations with staff out on Covid-related illness, whether with Covid itself or they’re isolating, and when I say operations I mean the main drivers, in Dublin Bus and Bus Éireann.
“What I am hearing anecdotally is up to 50 drivers at Dublin Bus are out and up to 30 or 40 in Bus Éireann, which will have an impact, of course, in its own right.”
Chief executive of the Restaurants Association of Ireland Adrian Cummins said the hospitality industry is very worried about Covid-19 again, as restaurateurs have seen an increase in staff shortages in the past three weeks.
“We are seeing an increase amongst staff being out with Covid at the moment. I presume that as we are seeing airline cancellations, especially with Aer Lingus, so if that company is seeing Covid we are going to see it across the country in every sector,” he said. “In hospitality, we can see it at the moment, our difficulty is if a chef is out with Covid then the whole business is under pressure.”