Air-traffic control delays affect 75 per cent more British Airways flights than prior to Covid, the airline has said.

The revelation is included in a letter to BA staff sent out today by senior management and seen by The Independent.

It begins: “Yesterday was one of the toughest days we and our customers have faced for many months.

“Last night saw us contending with strong winds, low visibility and repeated bands of torrential rain across the London Traffic Management Area and the surrounding area which resulted in lengthy delays to all airlines’ flights departing and arriving at Heathrow.

“Unfortunately, a number of aircraft yesterday evening couldn’t get timely air-traffic clearance to depart. The primary driver of this was air-traffic delays to departing flights, which left us with no choice but to cancel those flights at late notice, which is never a situation we want to be in.”

The letter goes on to say: “42 per cent of our flights this year [were] disrupted by regulations put in place by air-traffic control, up from 24 per cent in 2019.” That equates to 75 per cent more BA flights disrupted due to air-traffic control restrictions than before Covid.

The British Airways letter to staff says: “We’re working with [air-traffic control provider] Nats to learn lessons from our recent experiences so that together, we can build additional resilience for our customers and you, our colleagues.”

A spokesperson for Nats said: “Yesterday’s weather was as everyone knows, shocking and so there were weather-related air traffic control regulations in place.

“These temporary restrictions are only ever applied to maintain safety. Our chief operating officer met with British Airways and Heathrow on Monday 23 September and we have all committed to do an open-book data analysis to mutually understand how our operations can work together to minimise disruption during challenging operational days.”

Air-traffic control (ATC) is also under fire from Ryanair. In a statement today, Europe’s biggest budget airline said: “On Friday 27 September, 16 per cent of Ryanair’s first wave departures, representing 93 of 569 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.”

A spokesperson for the pan-European air-navigation coordinator Eurocontrol said: “The air-traffic situation today is very different from and more complex than the air-traffic situation in 2019.

“Eurocontrol is working with all aviation partners to address the situation collaboratively.”

The British Airways letter to staff also points a finger at the aircraft engine manufacturer Rolls-Royce, saying: “We’ve also had to make a number of cancellations to our 787 schedule over the next 10 days, as we continue to experience delays to the delivery of engines and parts from Rolls-Royce – particularly in relation to the Rolls-Royce Trent 1000 engines fitted to our 787 aircraft.

“We’ve apologised to customers and thankfully are able to offer the vast majority a flight the same day, either travelling with us or one of our partner airlines.

“We’re sorry for the impact that this is also having on you. We continue to work closely with Rolls-Royce to ensure the company is aware of the impact its issues are having on our schedule and customers, and seek reassurance of a prompt and reliable solution.”

A spokesperson for Rolls-Royce said: “We continue to work with British Airways and all of our customers to minimise the impact of the limited availability of spares due to the current supply chain constraints.

“Unfortunately, this is an issue affecting the whole aerospace industry.”

On Friday, British Airways has so far cancelled more than 50 short-haul flights to and from London Heathrow, including multiple links with Belfast City, Edinburgh, Glasgow and Paris CDG.

Four more flight cancellations were made by other airlines at Heathrow early this morning: to Brussels, Dublin, Geneva and Venice.

BA has grounded Friday’s long-haul services to Chennai and Delhi in India, as well as transatlantic departures to Baltimore-Washington and Las Vegas. All but the last were due to be operated by an older type of Boeing 787.

During the week British Airways faced criticism for its Gatwick airport operation after two passengers were wrongly turned away within hours for supposed passport infringements.

BA has apologised to the customers and will pay appropriate compensation as well as reimbursing their costs.