Travellers face disruption threat due to air traffic controller shortage

Airline passengers could face delays and cancellations this summer because of staff shortages in UK air traffic control rooms which may cause problems for years, aviation experts fear.

Travellers may suffer last-minute disruption because National Air Traffic Services (Nats) has been struggling to replace retiring controllers, insiders have warned. More than a third could leave in the space of five years.

Staff shortages led to hundreds of flights being cancelled throughout last summer, affecting Gatwick, Heathrow and Glasgow airports. Nats believes its workforce will be sufficient this year but Ryanair says the situation is still “unacceptable”.

Concerns also remain about the ageing Nats computer system. This left thousands of passengers stranded in chaotic scenes last August when it suffered a rare glitch and airliners had to be grounded.

Staffing is the most pressing issue, however, and one retired controller who still has contacts serving at Nats told i that it “will go on for a couple of years at least”.

“The situation isn’t going to get dramatically better any time soon, so delays and cancellations won’t either,” he said. “If demand goes up, it may well get worse.”

Aviation analyst John Grant of the travel data firm OAG agreed. “This summer will be tight, and indeed summers for the next few years,” he said. This “unfortunate situation” was the result of “really poor planning by Nats”, he added.

Industry insiders warn there could be more disruption to air travel caused by problems at Nats this year (Photo: Daniel Leal/AFP)

Nats admits the staffing situation is difficult but the part-privatised company argues it has been working urgently to address this.

It says that extra trainees and fewer retirements than expected recently, combined with lower air traffic forecasts and special overtime agreements, should provide enough controllers this year.

However, news this month of airlines expecting record bookings for summer flights will put further pressure on airport control towers and the Swanwick centre which manages London’s busy airspace.

Industry experts are at pains to emphasise that this does not pose a safety risk to the public. There are strict rules in the UK on how often controllers must take breaks, how long their working days are and how many flights they can each oversee.

But these high standards mean that when there are insufficient staff on duty, flights are delayed, diverted or grounded at short notice to ensure controllers can still do their jobs properly.

A serving controller who works in the south-east of England said: “There is a controller shortage, no doubt about that.”

He said that any disruption is not the fault of his colleagues, who are highly skilled and take pride in their jobs – but when there are absences, “bottlenecks” of delayed flights are unavoidable because “sectors get reduced down” in capacity.

Air traffic in the London region is controlled at the Nats centre in Swanwick, Hampshire (Photo: Nats)

Speaking to i, Nats chief operations officer Kathryn Leahy accepted that there is “no question” it will be “a busy summer”. “I am doing everything I possibly can with my teams to be ready to tackle that demand,” she said.

Ms Leahy wants to “protect” people’s travel plans, but added: “We are very transparent with our airport customers about the level of resourcing that we hold, where we may have challenging days, and how we adjust.”

Nats stresses that the vast majority of flights operate without any delays caused by its operations. It handles 24 per cent of European air traffic, but is responsible for just 1.5 per cent of delays.

Strikes by airport staff or European controllers, workforce issues at airlines or foreign airspace management centres, flight diversions caused by Russia’s invasion of Ukraine, and extreme weather, all pose bigger threats to the holiday plans of most British fliers according to experts.

When shortages do hit the UK’s air traffic control rooms, however, unlucky families can find themselves stuck for hours or even days while expensive and long-awaited itineraries are wrecked.

This is especially galling for the public because they count as “extraordinary circumstances”, meaning no compensation is paid by airlines for delays or cancellations.

Ryanair is scathing of the Nats leadership. A spokesperson for the airline said: “Nats air traffic control continues to be an inefficient shambles which threatens passengers’ travel plans… Repeated Nats failures are unacceptable and make clear that it is time for overpaid CEO, Martin Rolfe, to go and let someone competent take over.”

The problems have been raised in Parliament. Labour’s Baroness Ritchie alerted peers in September to the “immense inconvenience” suffered by travellers, following a series of “staffing issues which resulted in delays and cancellations”.

Nats handles about 2 million flights per year ‘in some of the busiest and most complex airspace in the world’ (Photo: Nats)

‘A perfect storm’  

Gatwick’s situation has been a particular concern. There have been continued medical absences in the control tower, which manages takeoffs and landings at the airport.

“Gatwick is a perfect storm,” the retired controller said. “They don’t have the people to man it, but they have to keep it safe.” This led to several days of flight groundings last year.

The airport suffers from the worst air traffic control delays in the UK, at an average of 1.45 minutes per flight, according to data released last year. That was way ahead of Heathrow, which came second with 0.67 minutes.

Analysts say that Nats has been unlucky at Gatwick. It only took on tower operations there in 2022, at short notice, and inherited a staffing shortfall from the previous contractor, Germany’s DFS.

Nats has been doing its best to fill the gaps at Gatwick’s control tower. It recently agreed a new overtime deal with unions and has filled all five training places there. It believes this will “significantly improve the situation”.

Solving the problems altogether may take time, however, given the challenges for new arrivals in getting up to speed.

Controllers all receive the same basic training at college but then spend far longer specialising in the unique and complex demands of their particular airport or region.

Gatwick is a difficult one to manage, with up to 55 aircraft taking off or landing on its single runway every hour. Even experienced controllers usually take nine months to learn the ropes and fresh recruits often need two years.

Ms Leahy said: “It would be like somebody doing their driving test on the Isle of Skye and then being thrown onto Birmingham’s spaghetti junction.”

This also means that just one or two unexpected absences from the team can be problematic, because it’s hard to cover for them.

Doug Maclean, a former air traffic controller who is now managing director of DKM Aviation Partners, told i: “Once you get the wrong side of that staffing curve at an airport, it takes months or even years to get back on the right side… You may have limitations on services.

“I’m sure they’re maximising efficiency as much as they possibly can, but there may simply not be enough people to do the job… We have a very safe system but that has penalties.”

A Gatwick spokesperson said that Nats has “successfully increased the number of air traffic controllers over recent months… We continue to work closely with Nats to further build on their numbers. Nats have assured us there will be the required resources to deliver this year’s busy summer schedules.”

Staff shortages at the Nats-run control tower at Gatwick caused many cancellations and delays at the airport last year (Photo: Nats)

The staffing crisis has been looming over Nats for some time.

Its most recent business plan, published in 2022, cautioned that if demand for flights was high, it “will not be possible” to train enough new controllers. This would “very likely to lead to service quality being degraded” for airlines and their passengers.

It included a graph indicating that it may need almost 950 full-time controllers to cater for high flight demand across the UK this summer, but might only have a maximum of around 850.

Its staffing resilience plan, published the same year, also warned: “There is a risk that even small levels of traffic growth may result in much greater increases in delay.”

It suggested there might not be enough capacity at Swanwick to meet demand for flights in and out of Gatwick, Stansted and Luton airports at peak times this summer.

Demand at Heathrow – one of the world’s busiest airports – may also surpass Swanwick’s capacity for the whole of next year, it added.

Nats says these “worst-case scenarios” are now unlikely, as it believes that peak air traffic may in fact be 10 per cent lower than previously predicted. But they are not out of the woods yet, according to experts.

Michele Robson, a former controller who is now editor of travel website Turning Left for Less, said: “Last year they just about got away with it. This summer there’s a chance of disruption, though they will try to mitigate it.”

Months of last-minute disruption

• 15 June 2023: Two flights from Glasgow are diverted and others are delayed because of air traffic control staffing problems.  
• 10 July: EasyJet cancels more than 1,700 flights from Gatwick over the summer, affecting more than 180,000 passengers. Various problems across Europe are blamed, but the airline also reveals that ATC delays on its Gatwick flights are three times worse than before the pandemic.  
• 12 July: Gatwick is ranked as the worst performer for ATC delays among 31 major European airports, according to official data. The airport claims that it has been “impacted disproportionately by disruption on the continent”.  
• 25 July: At least 70 flights at Gatwick are cancelled because of “last-minute staff shortages at the control tower” and bad weather over Europe.  
• 28 August: About 300,000 passengers suffer travel disruption when a Nats computer glitch causes more than 2,000 flight cancellations at major UK airports including Heathrow and Gatwick on bank holiday Monday. Some passengers are stranded abroad for several days amid a backlog of delays.  
• 14 September: ATC staff shortages at Gatwick lead to 42 flights being cancelled and hundreds more being delayed.  
• 23-24 September: More than 40 flights are cancelled at Gatwick over this weekend, and 164 more cancelled the following week, when nearly a third of staff at the control tower are off sick.  
• 19 November: At least 60 flights to and from Heathrow are cancelled, with two transatlantic flights also diverted, “due to short-notice staff absence in the tower and strong winds” – affecting more than 10,000 passengers.  
• 29 December: Further delays of up to two hours at the end of Christmas week lead to Ryanair complaining of eight instances of ATC staff shortages causing disruption at Gatwick in the space of a month.  

Tens of thousands of air passengers saw their flights cancelled or delayed on the August bank holiday last year after a Nats computer problem (Photo: Daniel Leal/AFP)

Retirement crisis  

Nats expects a huge chunk of its team – 25 to 35 per cent of controllers – to retire between the start of last year and the end of 2027.

Its staffing resilience plan cautions that they “can leave with relatively short notice”, in contrast to the “long lead times to recruit and train” their replacements.

Others are leaving their roles in the UK for higher pay abroad, especially in the Middle East where hub airports are expanding. Mr Grant says: “Some countries and airports are poaching qualified staff, which is why you see extended notice periods being applied.”

Reduced numbers aren’t the only problem. Naturally, those who are retiring or being headhunted tend to be the most experienced. This impacts “flexibility in deploying staff” while newer members are honing their skills, the Nats plan explains.

The retired controller who spoke to i said: “You can’t just magic people off the street and turn them into controllers in three weeks. You need two years. And the number of controllers over 50 is enormous in this country, so the number of people retiring is going to be enormous.

“They can’t get enough people through the college quickly enough and then trained at the individual units, because that takes 12 to 18 months and not everyone makes it.”

Nats has found it tricky to train enough new staff to replace those who are retiring (Photo: Nats)

“The situation isn’t going to get dramatically better any time soon, so delays and cancellations won’t either”

Retired air traffic controller

The lengthy induction process makes industry experts all the more frustrated that Nats controversially decided to release all 122 trainees from its college in September 2020.

Back then, the company explained: “There is no realistic scenario in which we will need further trainees from the college until 2022 at the earliest. In fact, we will not have any capacity to support further new trainees at Swanwick, our biggest operational centre, for the next two years.”

However, the union Prospect warned at the time that this decision may come to haunt the company. Accusing it of operating on a “boom bust” cycle, Prospect reminded the firm of “the very real impact that poor staff planning can have on our air traffic control capacity and in turn on passengers”.

The union’s national secretary, Steve Jary, complained of a “total lack of logic and short-termism” in laying off trainees when some were just four months away from qualifying. “After a downturn, air traffic returns with a vengeance,” he said.

Nats said it did not take the decision lightly and later rehired 90 per cent of the trainees. But it admitted in its 2022 documents that the pause means “we may not have adequate resource to meet all of our operational and training needs” in future.

Ms Leahy, the Nats COO, said: “We have every seat in our college filled, it’s a pipeline of new air traffic controllers.” The number of controllers it delivered last year for London operations in Swanwick was 8 per cent higher than the pre-pandemic figure.

She added that it would not have been possible to train staff properly during the pandemic, when there were too few flights to stretch and test their abilities. “You’re not allowed to pass people using a simulator. You’ve got to train in the live environment and there was no traffic during Covid.”

Safety worries in Europe and America

• Staff shortages are a problem for air traffic control networks around the world, raising concerns about air safety across the EU and the US.  
• Passengers in UK airspace are protected by strict regulations, which prevent British controllers being overloaded with flights to manage or overworked with too many shifts. This isn’t the case everywhere else, however.  
• Union leaders in Europe are concerned about the dangers caused by overworked staff trying to cover between 700 and 1,000 vacancies across the continent.  
• “We cannot push people continuously, and relying on overtime has its limits as well because we are in a safety-critical environment,” said Frederic Deleau, the executive vice president at the International Federation of Air Traffic Controllers’ Associations, speaking to Politico in August. “We cannot continuously ask people to come to work 12 hours or to work six out of seven days on a continuous basis without risking that at one stage they will overlook something or an incident will happen.”  
• In the US, there are concerns about the rising number of mistakes that could prove disastrous. Official figures show there were 503 “significant” incidents in American air traffic control in the latest annual figures, a year-on-year increase of 65 per cent.   
• Seven reports of controllers sleeping while on duty and five instances of them working under the influence of alcohol or drugs were revealed by a New York Times investigation in December.  
• Insiders told the newspaper that a combination of six-day working weeks, long shifts and rotas varying from early mornings to late nights is causing physical and mental health problems among the workforce, with some using sleeping pills to cope.  
• A spokesperson for the US Federal Aviation Administration said its team “maintains the safest, most complex and busiest airspace in the world”, and that recruitment will lead to “better working conditions”.  

The air traffic controllers working in airport towers have highly specialised knowledge and skills (Photo: Nats)

Elderly computer programme  

There are concerns within Nats that the ageing computer programme it uses to manage flights may also cause further disruption this year.

The company relies on the National Airspace System, which was developed in 1967, for flight data processing. It runs on modern computers but using archaic coding.

It was this system that broke down on August bank holiday last year, with Nats blaming “a logic error due to the software processing”. It was caused by “an extremely rare set of circumstances” when a flight plan used two waypoint markers that shared the same name. The sector’s regulator, the Civil Aviation Authority (CAA), is investigating.

“The computer system is very creaky,” the retired controller told i. “The system is quite old. It’s been remarkably resilient considering how ancient is.”

He added: “The interface we have worked with is really good, they’ve done a really good job with that. But the system which runs it needs replacement. And that’s proving really complicated.”

Concerns have been raised about this old system for years. As far back as 2014, Oxford computer expert Professor Martyn Thomas warned in a newspaper interview: “It wasn’t designed to cope with the volume of air traffic we have today, or to interface with modern computer software… Britain is now the only country that is using the 1960s software.”

A decade on from his comments, it is still in use.

While appealing to the CAA for higher airline fees last year to fund IT upgrades last year, Nats underlined the urgency of a “much-needed modernisation of our physical and airspace infrastructure”. But it argues that the current system is still safe and delivers the vast majority of flights to their destinations without causing delays.

Ms Leahy said: “I am acutely aware of our ageing [computer] systems. I am acutely aware that something may break. The key thing for me is how we respond to that breakage, how we communicate with customers, and the speed of us being able to get it back up and running.”

She argued it is impossible to completely eliminate delays, because no business has “absolutely foolproof” technology. But she added: “In the pipeline there is both a sustainment plan, which makes sure that they don’t fall over, and a replacement plan.” She expects this to be delivered by the end of the decade.

Radar screens in the Nats operations room at Prestwick, Ayrshire, which manages flights across northern England, Scotland and the north-east Atlantic (Photo: aviation-images.com/Getty Images)

“This summer will be tight, and indeed summers for the next few years”

John Grant, OAG

Airlines have complained about air traffic control fees rising by 26 per cent, to roughly £2.08 per passenger per flight. But the former controller said: “If the airlines want a resilient system and more controllers, someone’s got to pay for it.”

Nats announced a profit of £148m in June, however. It was part-privatised by Tony Blair’s Labour government in 2001, with 51 per cent of the group being owned by shareholders and the government holding the remaining 49 per cent.

Between 2011 and 2020, it paid out £550m in dividends to shareholders, although it paid out none last year.

The serving controller who spoke to i questions whether it should be passing money onto shareholders rather than investing it in upgrading systems and employing more staff.

“I cannot understand why it was ever considered to be a good idea that Nats was part privatised,” he said. “It is insane to me that something that’s such a fundamental part of the national infrastructure should be beholden to shareholders. That’s nuts.”

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Mr Maclean has similar worries. “Very few air traffic control services are privatised,” he said. “It doesn’t make a lot of sense.”

Ms Leahy said that Nats’ pricing, staffing and investment decisions are tightly regulated.

Nats has spent an average of £130m a year on “improving, upgrading and sustaining” its computer systems for 22 years, she said, with no funds coming from the taxpayer. “We are happy that we have got our settlement from the regulator that will deliver a safe and resilient service.”

Paul Smith, a director at the CAA, said: “Consumers deserve the best possible experience when they fly. We expect those delivering aviation services, including Nats, to take all possible steps to prepare for and manage forecast demand for air travel, including making sure they have sufficient staff to deal with busy periods. When delays occur, the industry should also make sure consumer are looked after in line with their rights.”

@robhastings