Noise

Zurich Airport Group understands that flight operations generate noise that affects the surrounding communities. Accordingly, it takes a number of measures to minimise the negative impact.

Relevance

Where noise arises and how loud it is perceived to be depends on a variety of interrelated factors. Generally speaking, the orientation of the runways and flight paths are key. These depend on the nature of the terrain and the prevailing weather conditions. The flight timetables of airlines and the aircraft fleets they deploy are further major factors. Advances in engine technology also have an effect, but these are controlled by the airlines and can only be influenced indirectly by the airports (incentives from noise charges). Of further relevance is the sharp increase in population in the airport region over recent decades, which has been above-average compared to the Canton of Zurich and Switzerland as a whole.

Noise is less of an issue for the company’s majority-owned subsidiaries in Brazil and Chile, where the volume of air traffic is much lower. In the case of Brazil, the number of flight movements at all sites is below the threshold as of which the government demands that noise be monitored. Moreover, most take-offs and landings in Brazil are over the sea, while the airports in Chile are sited well away from large conurbations. At the airport in Noida, India, the focus in the reporting year was on construction noise. This is monitored via corresponding measuring points. After the airport goes into operation, additional noise measurement points are to be installed.

Approach and progress

Zurich Airport Ltd. employs technical, structural, operational and financial measures to tackle aircraft noise, all of which are aimed at reducing noise at source and along propagation pathways. At Zurich Airport it seeks to ensure that noise does not exceed the emission limits in any residential areas outside the zone defined in the Sectoral Aviation Infrastructure Plan (SAIP). As the figures for the reporting year were not yet available on the date on which this report was published, the following information refers to target achievement in the previous year (2023). During the day (6:00 to 22:00), this target was achieved in 2023 as well as in 2022. In the first night hour (22:00 to 23:00), the relevant area was reduced from 16.9 ha in 2022 to 5.7 ha in 2023. This can be attributed to changes in meteorological conditions, which made it possible to apply noise-optimised operating concepts more frequently. In the second night hour (23:00 to 5:00), however, the area increased significantly from 60.8 to 114.8 ha in 2023. The reason for this was the increase in delays.

In addition, the sound insulation programme includes various passive noise mitigation measures which Zurich Airport Ltd., as the originator of the noise, is obliged to put in place in Zurich. These include in particular the installation of sound-insulating windows in living rooms and bedrooms. The company is aiming to roll out sound insulating measures in at least 200 further properties a year between 2022 and 2026, or alternatively to reimburse homeowners. As in recent years, this target was also met in 2024.

Communication with local residents

Zurich Airport Ltd. is aware that aviation noise can be perceived as a nuisance and that the public has a need for information. Transparent information and dialogue with residents and organisations are vital. The company has therefore reported on noise statistics and flight operations for a number of decades already. For instance, the number of take-offs and landings at the Zurich site, broken down by runways and flight paths, is reported on the company’s website each day. Residents affected by aircraft noise can call or use an online form to contact Zurich Airport Ltd. with any queries or concerns, and staff from the Noise Management department respond to specific questions.

Besides individuals, a number of bodies including municipalities in the airport vicinity, the Canton of Zurich and other neighbouring cantons, districts across the border in Germany and a variety of agencies and citizens organisations concerned with air traffic noise make representations to Zurich Airport. The company maintains a regular dialogue with these groups too.

In the reporting year, the number of enquiries and complaints increased by roughly 3% compared to the previous year. The most common cause of enquiries and complaints were take-offs to the north and evening flights from the south (see Noise statistics).

Noise exposure is less of an issue in Latin America. Nevertheless, channels are provided at each of the airports in Brazil, to offer noise information and receive complaints. The environmental licences of these airports are subject to the obligation to set up an easily accessible digital hotline for noise complaints and to submit quarterly reports to the authorities. See the Business ethics section for more information.

Noise monitoring

In order to objectively assess the noise situation and levy noise-related charges, it is necessary to have accurate measurements of noise levels. Data on air traffic noise in the vicinity of Zurich Airport have been collected since 1966. A network of noise monitoring stations currently at 14 fixed locations near arrival and departure routes is operated. The system automatically links the noise data recorded by these monitoring stations to the corresponding flight movements. These data are published monthly in a noise bulletin that can be freely accessed on the company’s website. As prescribed by the Sectoral Aviation Infrastructure Plan (SAIP), aircraft noise exposure and the progress of mitigation measures are analysed in a comprehensive report each year which is submitted to the Federal Office of Civil Aviation (FOCA). This report is then used as the basis for taking corrective action (see night flights and special authorisations).

The number of take-offs and landings increased by 6% year-on-year in the year under review. It was nearly back to 2019 levels at the end of 2024. Accordingly, an equivalent or higher level of aircraft noise than in the previous year was recorded during daytime hours at the four main monitoring stations. However, the figures did not reach the 2019 level at all monitoring stations.

The diagram above shows changes in exposure to aircraft noise at Zurich Airport over time. It shows the noise contour emission limits for residential zones for various years, with the enclosed area representing threshold breaches. The comparison shows a reduction in the area over the years and hence a reduction in noise exposure despite a steady rate or increasing amounts of air traffic. This can be attributed to technical advances in aircraft design resulting in lower noise emissions. It should be noted that demand had not yet fully recovered in 2023 since the pandemic and that noise levels for flights arriving from an easterly direction differ due to changes in westerly winds from year to year. The noise contours for the reporting year will not be available until mid 2025.

Flight path monitoring

Take-off routes from Zurich Airport were configured to avoid low overflights of densely populated areas wherever possible. The Noise Management unit monitors all aircraft departing Zurich Airport for adherence to the prescribed flight paths. These are mandatory during daytime at least up to an altitude of 5,000 feet (approx. 1,500 m above sea level) and at night up to flight level 80 (approx. 8,000 feet or 2,500 m above sea level). A monitoring system is used to check compliance with the flight routes.

An aircraft may only deviate from the prescribed flight path if there is good reason to do so, for instance to avoid storm clouds or following instructions from an air traffic controller. If there is no legitimate reason, an investigation is triggered, and the pilot in question will be asked to submit a statement in writing. These investigations often also involve interviews with representatives of the airlines. If the investigators are not satisfied, the matter may be referred to FOCA. This constant monitoring encourages the airlines to optimise the take-off phase at all times.

As in the previous year, the most frequent reason for deviations from the prescribed flight paths were specific instructions from air traffic control. A total of 145 (2023: 132) investigations into unjustified deviations were launched, and 29 (2023: 38) interviews were held with chief pilots.

Night flights and special authorisations

Residents living near Zurich Airport perceive night-time flights to be particularly intrusive. Complaints are most often received about flights after 23:00. The reasons for delays in 2024 were primarily related to air space restrictions in the eastern European and Middle Eastern crisis regions with effects (increased traffic) on surrounding air traffic control, in particular in Germany. Bottlenecks in European air traffic control also contributed to the delays. Together with its partner companies, Zurich Airport Ltd. is currently implementing a programme of measures to reduce the number of flights after 23:00. Due to the lengthy decision-making and approval procedures, it is not yet possible to implement the key measures that would bring about a lasting improvement, such as better separation of take-off and approach routes, straight starts on runway 16 during “bise” (cold dry north wind), or extending the two shorter runways. Short to medium-term measures include planning for and providing sufficient personnel throughout the passenger and freight preparation process and optimising operational processes. The request filed on 10 December 2024 with FOCA for reclassification of the noise classes and an increase in the noise charges for the second portion of the night should help to improve the delay situation.

In 2024 3,389 flights (2023: 3,506) were operated at night (23:00 to 06:00). A total of 411 flights (2023: 310 flights), operated during the night-time curfew period (23:30 to 06:00) were given special authorisation. These night flights are authorised only for legitimate reasons (see Noise statistics). The large number of night flights was due to restrictions in the European airspace, technical aircraft malfunctions, difficult weather conditions, the Ukraine peace conference and IT outages at partner companies (some of which were global). However, delays caused by personnel shortages at partner companies were reduced significantly versus previous years.

Use of the noise protection hangar

The noise protection hangar helps to significantly reduce noise from engine ground testing. Engines from aircraft up to the size of a Boeing 747-800 can be tested in the hangar. Although it significantly reduces noise exposure for nearby residents, the hangar does not completely eliminate the noise so there are set limits for the number of tests that may be run.

In 2024 a total of 449 (2023: 416) engine ground tests were carried out in the noise protection hangar. According to the Federal Noise Protection Ordinance (Lärmschutzverordnung, LSV), the period falling between 19:00 and 07:00 counts as night-time for the purpose of assessing idling noise. Out of the 131 idling processes carried out during the night, 79% related to short and medium-haul aircraft and business jets. On the other hand, wide-body aircraft were tested in most instances during the day between 07:00 and 19:00. The permitted noise exposure level was exceeded six times. The breaches were caused by extended full-throttle tests during the night between 19:00 and 07:00. According to the agreement concluded with the neighbouring municipalities, the permitted level may not be exceeded more than 25 times during any given year. No engine idling above idle power level tests were carried out during the reporting year outside the hangar.

Noise charges and Airport Zurich Noise Fund

Levying noise-related charges gives airlines a financial incentive to operate the quietest possible aircraft on their Zurich routes. All jet aircraft are assigned to one of five noise categories, each of which has a different charge rate based on the time of take-off and landing. In addition, shoulder and night surcharges are applied to flights between 21:00 and 07:00. These may vary according to noise class and the specific take-off or landing time.

Until the end of 2020, all income from noise charges was credited to the Airport Zurich Noise Fund (AZNF). AZNF funds are used primarily to cover the costs of noise mitigation measures, in particular the sound insulation programme, the south-side sound insulation concept, and the costs of meeting compensation claims for noise and overflying. As the law currently stands, the AZNF has sufficient assets to cover the known future costs for these purposes. Since then, therefore, revenue from aircraft noise charges has been reallocated to the “Aviation” segment. Further details about AZNF can be found in Note 20, Airport Zurich Noise Fund.

A total of CHF 16.0 million in revenue was generated from aircraft noise charges in 2024. Of this, CHF 6.7 million were from standard charges applicable to all 24 hours and CHF 9.3 million from surcharges levied during shoulder periods and at night.

Sound insulation

As the airport operator, Zurich Airport Ltd. is obliged to pay the costs of sound insulation measures in properties in the communities around Zurich Airport that are exposed to excessive aircraft noise. This is primarily for installation of sound-insulating windows as part of the noise protection programme. Property owners who have already taken the initiative of fitting sound-insulating windows themselves are reimbursed by Zurich Airport Ltd. The company met its target of installing sound-insulating windows in at least 200 further properties a year between 2022 and 2026, or alternatively of reimbursing homeowners in the year under review with 252 properties (properties with their own house number).

In addition, in areas where night-time noise exposure limits are exceeded, the company is offering owners the option of installing automatic window-closing systems or sound-absorbing ventilators. Owners of properties with bedrooms which are located within a clearly defined perimeter, and which were not subject to any obligation to install sound insulation during construction or conversion, are eligible to benefit from these passive noise mitigation measures.

Zurich Airport Ltd.’s south-side sound insulation concept is designed to prevent local residents being awoken by early-morning inbound flights from the south. At the request of owners, the company will install automated window-closing systems or sound-absorbing ventilators in bedrooms in the areas affected. After phase 1 was completed, FOCA published its decision on phase 2 of the south-side sound insulation concept with a larger perimeter on 19 January 2021. After an objection was raised by a neighbouring community seeking to have the perimeter further extended to include the whole municipality, the case is now pending before the Federal Administrative Court.

As part of phase 1 of the south-side sound insulation concept which was completed earlier, approximately 1,100 window-closing systems and 900 sound-absorbing ventilators were installed in bedrooms between 2016 and 2018. The total costs amounted to around CHF 3 million. In the year under review, work began on the first stage of phase 2. By the end of 2024, the current status assessment and project planning was completed in Wallisellen and Zurich Schwamendingen at 94 properties. Of these, measures were implemented in 29 properties.

Noise compensation (formal expropriations)

As air traffic noise can affect the value of a property, the company is faced with around 20,100 claims for compensation from property owners around Zurich Airport. The compensation claims were submitted at the time the airport was privatised and following the imposition by Germany of restrictions on flight approaches over its territory. Any new claims may now only be submitted if there are substantial changes to flight operations; as a result no further claims have been submitted to Zurich Airport Ltd. since then. Of the compensation claims received, by the end of 2024 15,042 (75%) had been concluded, with CHF 90.2 million being paid in noise compensation. All noise compensation claims are paid from the Airport Zurich Noise Fund (AZNF).

As there are very few provisions regarding noise compensation or direct overflights in federal legislation, every open question of law must first be tested in the relevant courts. Legal test cases are being conducted in the interests of processing outstanding claims efficiently. They are helpful both for clarifying questions of law and for obtaining legal rulings regarding the specific situation in the various airport regions.

Noise statistics for Zurich Airport