More than 10,000 airline passengers suffered flight cancellations because of bad weather and air traffic control (ATC) restrictions.
British Airways axed 51 fights due to operate to or from Heathrow on Sunday, and a further 31 on Monday.
Several airlines also cancelled Gatwick flights. The worst affected was easyJet, with 34 flights grounded on Sunday and at least nine on Monday.
Affected passengers are unlikely to be eligible for compensation as the disruption is deemed to be out of airlines’ control.
But they are entitled to assistance, which could involve refreshments, overnight accommodation and rebooking with alternative carriers.
A British Airways spokesperson said: “Due to air traffic control restrictions and adverse weather, like other airlines we’ve had to make a small number of alterations to our schedule.
“We know this will be frustrating for our customers and our teams are working hard to get them on to alternative flights as soon as possible, with the vast majority already booked onto services that will fly later today.”
Two British Airways aircraft were taken out of service for safety checks on Sunday after they were struck by lightning.
An easyJet spokesperson said: “EasyJet operated around 1,800 flights yesterday and is operating a similar number today, however, some flights yesterday evening and three flights from London Gatwick this morning have unfortunately been disrupted due to the knock-on impact of adverse weather and air traffic control delays.
“While this is outside of our control, we are sorry for the inconvenience caused and are providing impacted customers with hotel accommodation and meals as well as a refund or a transfer to an alternative flight.”
Ryanair avoided cancelling UK flights but suffered delays, which it blamed on ATC.
In a message on its website, the airline said: “ATC services, which have had the benefit of no French ATC strike disruption this summer, continue to underperform (despite flight volumes being 5% behind 2019 levels) with repeated ‘staff shortages’.
“On Monday 8 July, 21% of Ryanair’s first wave departures (134 of 579 aircraft) were delayed due to ATC ‘staff shortages’.
“These repeated flight delays due to ATC mismanagement are unacceptable.
“We apologise to our passengers for these repeated ATC flight delays which are deeply regrettable but beyond Ryanair’s control.”