The European Air Traffic Control services strikes expected over the next two days in Portugal and Italy will have a significant impact on flights, according to easyJet.
The airline said it had pro-actively re-timed some flights later into and out of Lisbon in order to avoid the strike period as well as re-timing some flights to and from Milan Malpensa.
"Like all airlines flying to/ from/and over these countries, we expect it will have a significant impact on our flights during these periods.easyJet would like to reassure passengers that it will do everything possible to minimise any inconvenience for passengers," easyJet said in a statement.
British Airways (BA) have also retimed and cancelled a number of flights to and from Italy, a spokeswoman said.
"We are doing all we can to minimise disruption to customers affected by air traffic control strikes across Europe. We are advising customers on short-haul services to keep checking the very latest information on our website," said a spokesman for BA.
easyJet said the industrial action is likely to continue into Thursday with the French Air Traffic control staff taking part.
More top news
Comcast said its cash offer is worth £12.50 a share – a 16% hike on the £10.75 a share offered by 21st Century Fox.
The Duke of Cambridge said the new prince was "behaving himself" and sleep was "going reasonably well so far".
The challenge came as Theresa May vowed no stone would be left unturned in putting right the status of the Windrush generation.