New Aircraft Separation System At London Heathrow Has Reduced Delays & Carbon Emissions

London Heathrow has introduced a new aircraft separation system that air traffic control provider National Air Traffic Services (NATS) says is already improving punctuality and cutting carbon emissions. The system was deployed in December 2024 as part of Heathrow’s existing Intelligent Approach arrivals spacing tool.

Heathrow is the first airport in the world to use the technology, which was developed by NATS and Leidos UK. The approach changes how the gap between arriving aircraft is calculated, and early results point to smoother operations at one of the world’s busiest and most capacity-constrained airports.

Data Shows Fewer Delays After Pairwise Introduction

The new system, which is known as Pairwise, replaced the traditional method of spacing aircraft, which used to be based on six categories that considered an aircraft’s weight and the wake it creates as it flies. Instead, it uses the exact characteristics (such as weight, speed, and wingspan) of each aircraft type, which allows controllers to shorten the gap for certain aircraft pairs without affecting safety. That extra efficiency means slightly more arrivals each hour and less time spent in holding patterns.

NATS data for the first six months shows arrivals with no delay increased from 17.8% a year earlier to 24%. Average arrival delays fell from 5 minutes 55 seconds to 4 minutes 46 seconds, and carbon emissions per flight dropped by about 19%. As a result, Heathrow has become Europe’s most punctual major airport so far this year. Gary Harman, Head of Punctuality and ATM at Heathrow, said:

“Making sure passengers arrive on time is fundamental to making every journey better. Working with NATS, we can already see the incremental improvements that Pairwise is helping to deliver. It’s no secret that Heathrow is operating at capacity, and innovations like this are a great way to improve punctuality and resilience while reducing our impacts.”

Pairwise Builds on Intelligent Approach Introduced In 2015

Pairwise is part of the wider Intelligent Approach arrivals spacing tool that Heathrow introduced back in 2015. That system uses time-based separation to adjust gaps between arrivals according to weather conditions. According to NATS, it has reduced delays caused by headwinds by more than 60% and cut annual carbon emissions by over 45,000 tons annually.

Furthermore, its introduction comes as the air traffic controller continues broader work to improve operational performance across the UK network. The organization’s eighth annual Aviation Index, which was carried out by Ipsos UK, found that there is a growing expectation for the industry to improve performance and reliability. In June 2025, NATS safely managed 237,215 flights, up 2.5% from June 2024, and contributed just 1.2% of total European en-route delays, despite handling nearly a quarter of the continent’s air traffic.

Brendan Kelly, Head of Queue and Capacity Management Solutions at NATS, said: “Pairwise was another world first deployment for NATS, and while there are lots of factors that can influence operational performance, these interim benefits paint a very positive picture of the value it is delivering for Heathrow and our airline customers. Our job now is to continue evaluating the tool to understand where we can deliver even greater operational and environmental benefits over the busy summer period and beyond.”

Beyond Heathrow, the Intelligent Approach is also in use at Toronto Pearson International Airport and  Amsterdam Schiphol Airport. Additionally, in March, it entered service at  London Gatwick Airport as the first deployment of its kind at a single-runway airport.

Additionally, in May, the British air traffic controller announced a contract with Saudi Air Navigation Services (SANS), the kingdom's air navigation service provider, to introduce the tool at Riyadh, Jeddah, and Madinah airports. This will mark the first implementation of the Intelligent Approach in the Middle East.