Air traffic controller staff absences and high winds reportedly forced dozens of flight cancellations at Heathrow on Sunday.
The ATC restrictions limited the number of aircraft that could safely take off and land per hour and applied to all airlines.
Two inbound transatlantic flights had to be diverted to Gatwick and Stansted while other services faced delays.
The majority of cancelled flights were reported to be British Airways short-haul services, while other airlines were also affected, including Aer Lingus, Brussels Airlines, KLM, Lufthansa, SAS and Swiss.
National Air Traffic Services (Nats) said that staff shortages were also a factor in addition to the weather.
A spokesperson told national media that “temporary air traffic control restrictions” had been put in place on Sunday “due to short notice staff absence in the tower and strong winds at Heathrow”.
Nats added that it had been working hard with the airport and airlines to minimise disruption: “Restrictions of this sort are only ever applied to ensure safety and we apologies for any inconvenience caused.”
Heathrow said “minor changes” were made to Sunday’s schedule as a result of the weather.
A BA spokesperson said: “Air traffic control restrictions imposed on all airlines at London Heathrow required us to make some adjustments to our short-haul schedule.
“We contacted affected customers to apologise and offered them rebooking options or a full refund.”
A handful of BA short-haul departures from Heathrow were cancelled this morning, including to Barcelona, Zurich, Toulouse, Basel and Nice.
The BA spokesperson said: “Industrial action by French air traffic control staff means we’ve had to make some adjustments to our short-haul schedule. We’re in contact with our customers to inform them of their rights and offer them options including a full refund or rebooking onto an alternative flight.”
This came as Ryanair renewed a demand for the European Union to step in to protect services flying over France affected by today’s strike by the country’s air traffic controllers.
The industrial action has resulted in the cancellation of a quarter of flights at Paris-Orly and Toulouse airports and 20% at Bordeaux and Marseille.
A Ryanair spokesperson said: “It is completely unacceptable that there have been 65 days of ATC strikes this year – 13 times more than in all of 2022 – which have caused the cancellation of thousands of flights at short notice, unfairly disrupting EU passengers’ travel plans.
“Despite repeated calls on [European Commission president] Ursula von der Leyen to protect passengers and overflights during these ATC strikes, she has failed to take any action to do so.
“As a result, even more passengers will have their flights cancelled at short notice due to this French ATC strike on Monday, despite not even flying to/from France. This is because France unfairly uses minimum service laws to protect French flights while forcing cancellations on overflights from Germany, Spain, Italy, Ireland and the UK.
“We have no problem with French ATC unions exercising their right to strike, but the EU Commission should insist that cancellations due to French ATC strikes are allocated to French flights, not those overflying France en route to another unrelated EU destination.”
EasyJet said: “We expect that there will be delays and some disruption due to the industrial action, therefore we advise all customers to check the status of their flight on our flight tracker.”
Jet2.com said: “We will be working hard to ensure that the impact on our flights is minimal, however, you may encounter some disruption if you are travelling during this time. Please be prepared for possible longer than normal waits onboard your aircraft to depart.”