Airlines using the UK’s busiest airports face up to three weeks of disruption due to a “challenging” revamp of air traffic control.
Travellers could be delayed by 20 minutes on flights bound for Heathrow and Gatwick as new airspace technology is introduced to replace a 1970s-style paper-based system, The Times reported.
The change, starting on Wednesday morning, will affect some of the 360,000 passengers travelling on about 2,300 flights a day in and out of the country’s busiest airports.
There may also be minor delays into Stansted, Luton and London City, controllers said.
More aircraft will be expected to land late at night or in the early hours, potentially causing more disturbance for households under flight paths.
The disruption is expected because controllers’ workloads are being reduced during the transition to an electronic flight management system.
Air traffic controllers based the national air traffic control service in Swanwick, Hampshire, currently use handwritten paper strips to record details of flights entering airspace in the south-east of England. Nats said the system had largely been unchanged for 40 years.
It will be replaced from tomorrow by electronic technology known as EXCDS, or extended computer display system, which digitises the process as part of a wider £1 billion ten-year upgrade.
Nats said that the change would ultimately allow controllers to handle more aircraft over London and the south-east, some of the most congested airspace in the world.
The change will have an impact on passengers for the first ten days, with the possibility of lesser disruption for a further ten days after that.
Flights could be delayed for up to 20 minutes into Heathrow, which handles about 1,400 a day, during the transition period. Aircraft will be expected to join holding patterns over London, slow on the approach to the UK or delay take-offs to limit the number of landings each hour.
Delays at Gatwick, which handles 900 flights a day at this time of year, will be up to 10 minutes.
Nats said that months of planning have gone into making the process “safe and predictable” and it was working very closely with airports and airlines to put in place measures to minimise any disruption to passengers.
“However, we do expect some flights to experience delays,” the air traffic service said.
“This is because we will be reducing the amount of air traffic in the transitioning sectors to give controllers more space to build up their confidence using the new tool in the live environment. We apologise in advance to any passengers who are affected.
“We also know there will be some impact on the communities around Heathrow and Gatwick who may hear flights earlier in the morning or later at night during the first ten days of the transition.
“We’ve asked the government for some flexibility on the usual limits so that we can land a small number of flights slightly earlier and slightly later than usual. We will do all we can to avoid this but we thank residents close to these airports for their understanding while we make this important change.
“This is a challenging project and we’ll be doing everything we can in the next few days to, first and foremost, keep everyone safe and to keep the traffic moving as efficiently as we can.”
NATS Control Centre, Swanwick, director Jamie Hutchinson said there were 285 controlers to train.
“For this significant transition we are forecasting up to 20 minutes of delay per flight for the first ten days and around ten minutes of delay per flight for the following ten days,” he said.
“That is for the flights that are delayed as a result of the transition but for the majority of UK flights there will be no impact.
“In order we have a smooth transition to the new system we do need to reduce capacity. We will be at 80% for the first ten days, 90% for the following ten days before we return to normal operations. It is important for the controllers to get comfortable and confident in the system.”