Thousands of flights have been cancelled or delayed due to anti-austerity strikes and protests across Europe called by the European Trade Union Confederation (ETUC).
Iberia, Iberia Express, Air Nostrum, Vueling, Air Europa and EasyJet have cancelled around 600 flights in Spain including flights to 250 international routes.
Portuguese airline TAP has cancelled more than 170 flights and most of the flights cancelled serve international routes.
39 flights have been cancelled at Heathrow with British Airways scrapping flights to Madrid and Barcelona and return services to Portuguese capital Lisbon, while 13 flights have been cancelled at Gatwick Airport.
London Heathrow Airport spokeswoman said most people seem to have got the message that some flights were going to be axed and the terminals are operating smoothly.
"Flight cancellations are never good news, but we do operate around 1,300 flights a day so the figure of 39 is a comparatively small one," spokeswoman added.
The cancellations include EasyJet's 26 flights within Europe, mostly to or from Spain, while other flights towards Greek were re-scheduled.
EasyJet said in a statement that it has been proactively trying to minimise disruption.
"However, we would like to warn customers that they could experience delays to their travel plans," the airline said.
British Airways spokesman said that the airline was also looking at putting on larger aircraft to help as many customers as possible.
"We are doing all we can to minimise the disruption to our customers," spokesman said.
"We apologise to our customers for any inconvenience caused by industrial action, which is beyond our control."
Ryanair has revealed that none of its flights had been scrapped yet.
Unions and activists from Spain, Greece, Portugal, and Italy in addition to 23 European nations participated in the move against rigid fiscal strategies launched by governments in the region.
ETUC said in a statement that austerity is a total dead end and must be abandoned.
"Social protection and wages can no longer be sacrificed," ETUC added.
Image: Several flights at Heathrow Airport were affected due to anti-austerity protests in Europe. Photo: courtesy of LHR Airports Limited.