Then, less than two weeks ago, British Airways joined the fray with a letter to staff that blamed Nats for the failure of many of its jets to get away from Heathrow on Sep 26, despite being granted an operating extension after weather-related delays.
The letter from two senior executives read: “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. This was incredibly frustrating for us and tough on our customers.”
BA also revealed that 42pc of its services had been hit by interventions from Nats so far in 2024, a sharp rise from the 24pc recorded in 2019, the most recent year to see a similar number of flights.
Wizz Air, which has a base at Gatwick, said Nats-related issues contributed to almost 300,000 minutes of delays across its network in July and August.
Marion Geoffroy, the UK managing director, said: “This summer was continuously challenging from an air traffic control perspective.”
However, she added: “After a difficult start we did see some improvement and we hope this trend continues.”
From the outside at least, it would seem Britain’s biggest airlines are now in open warfare with the head of a regulator meant to ensure the smooth passage of planes above our heads.
Nats has generally been reluctant to defend itself openly. It is a public-private partnership owned by the Government, pension funds and airlines, including easyJet and BA, meaning it prefers to keep a low profile that won’t upset the apple cart.
However, stung by the latest rebukes, Nats told The Telegraph that it has been directly responsible for only a small proportion of hold-ups. In fact, it claimed that reliability has markedly improved. Instead, it blamed stormy weather over summer for the increase in disruption – something it has no control over.
Despite handling the highest proportion of traffic in Europe, Nats has been responsible for fewer than 1.5pc of the delays in the region, it said, citing figures from Eurocontrol.
Moreover, 98pc of flights in UK airspace since April have experienced no Nats-attributable delay, it claimed, and even where there were hold-ups the average delay has been no more than 15 minutes.
The organisation also shot back at airlines, seeming to suggest that they had overfilled schedules to unrealistic levels.
It said: “Nats does not manage airline schedules. We share as much information as we can with the airlines and it is then up to them to decide what changes to make to their operation.
“We hold a daily ‘lookahead call’ to give as much information as we have on the following day and the potential impact that anything such as weather or capacity constraints may have so that operators can take that info away to help their planning.”
Nats also rejected suggestions that it is short of personnel following Covid, when the grounding of most flights led many senior personnel across the aviation sector to retire.
It said: “Nats does not have a staffing crisis. We have the correct numbers of controllers and engineers in our centres and at major airports.”
The only exception, it said, is in the control tower at Gatwick. Even there, performance has improved as more new staff complete the two years of training required to oversee takeoffs and landings at the world’s busiest single-runway hub, Nats said.
A spokesman added: “Everyone knew we had inherited a shortage of controllers that would take time to fix. We have a full training pipeline in place and are now close to the right number of fully valid controllers.”