A survey into Luton Airport’s flight paths has found they met their objectives in mitigating the impact on St Albans district – despite opposition from noise campaign groups.

The RNAV GPS navigation system was introduced in 2015 and narrowed flight paths, which anti-noise campaigners said simply concentrated noise pollution from flights over a smaller area.

The Civil Aviation Authority (CAA), have published the results of a post-implementation review (PIR), which analysed the impact of RNAV between its introduction and 2017.

The report concluded that the airspace change achieved the objectives set out in the original proposal.

A CAA spokesperson said: "The purpose of a Post Implementation Review is for the CAA, as the independent regulator, to assess whether the change has delivered the anticipated impacts and benefits set out in the original airspace change proposal and decision, and if not, to ascertain why and determine the most appropriate course of action.

"It is not a review of the decision itself, and neither is it a re-run of the original decision process."

The report found that the introduction of RNAV reduced planes directly flying over Redbourn, Hemel Hempstead and the southern areas of St Albans. As a consequence, however, the CAA found that the majority of departures had moved closer to Harpenden, south Harpenden and the less densely-populated areas of Redbourn, while still managing not to fly directly over those areas.

Aircraft movements increased by 30 per cent between 2015 and 2017, but the report claimed changing the flight paths was not an "enabler" for an increase in airport capacity, or for an increase in flights during the early morning and late evenings.

Therefore the report claimed the increase in noise complaints during that period was due to an increase in air traffic - implemented by the airport and its parent company London Luton Airport Limited (LLAL) - not the narrowing of the flight paths.

St Albans MP Daisy Cooper has slammed the CAA report as "passing the buck" by laying the blame of aircraft noise elsewhere.

She said: "This report is a blatant attempt to pass the buck as residents are being left to suffer as different authorities play the blame game.

"The CAA is taking the stance that they are responsible for the routes, not how many aircraft use the routes, which is a planning matter for Luton Borough Council and government policy.

"I have secured a meeting with the aviation minister and we will be raising our concerns in the strongest possible terms."

Anti-noise campaigners have also criticised the report for blaming the rise in complaints on an increase in flights, without acknowledging their belief that concentrating the flight paths exacerbated the problem.

John Hale, of St Albans Quieter Skies, said: "We are very disappointed by the CAA report. By blaming the increase in complaints just on the increase in flights, it ignores the fact that concentration makes people aware of many more aircraft, even though less may be going directly overhead. They've chosen the easy option to avoid looking into the real issue of whether concentration is a good thing or not.

"The CAA has also sidestepped the question about whether flights from London Luton Airport have more adversely impacted our communities since the introduction of RNAV.

"The report focuses only on the technicalities, and does not test all the claims by the airport about the noise reductions which would result from its introduction.

"Given the overall bad experience of the last four years, proposed additional expansion of the airport will just further damage our environment."

The CAA acknowledged that aircraft are still being dispersed over St Albans and south Harpenden, and reported a large reduction in noise over Sandridge - the accuracy of which has been disputed by campaigners.

Andrew Lambourne, of campaign group LADACAN (Luton and District Association for the Control of Aircraft Noise), said: "The assessment conveniently ignores the CAA's own guidance for what counts as an overflight: when an aircraft passes close by it is about as noisy as when it is directly overhead, making concentrated tracks close to communities a menace.

"The CAA has dodged all the difficult issues we raised with them in 2017.

"The whole thing feels like a rubber-stamping exercise, and was not worth waiting three years for," he added.