Airlines

Aviation activity has many benefits to society such as allowing people to freely travel for business and pleasure. However, like other forms of transport, aircraft do cause environmental pollution.

This can be categorised as follows:

• noise that can cause annoyance and in some cases health problems for local residents
• pollutants that contribute to climate change pollutants that affect local air quality
• other local impacts to the environment from running and maintaining aircraft that can impact local wildlife, habitats and water quality.

The level of environmental effects

Broadly speaking the more aviation activity that occurs, the greater the quantity of the pollutant – so the larger the airline, the higher the environmental impact. However, looking only at absolute levels doesn't tell the whole story. Per passenger pollution levels can also be considered, as can improvements in efficiency and performance. An airline that only used older, less environmentally friendly aircraft might create more noise and air pollution per flight than a larger airline.

Airlines publish information about their environmental impact in terms of:

• Greenhouse gas emissions
• Noise

Unfortunately, some techniques and procedures designed to reduce one environmental effect can lead to an increase in another environmental effect, for example by avoiding flying over more densely populated areas to reduce noise impacts can increase the journey distance which will increase the amount of emissions it generates.

The government has issued guidance to the CAA setting out a policy where noise should be prioritised over climate change at lower levels of altitude and vice-versa at higher altitudes. Read the government guidance.

The factors that can vary the impact on the environment

Like with other forms of transports such as road and rail; many factors affect the environmental impact of taking a flight. Generally speaking the more fuel-efficient an aircraft is the better for the environment. However, many factors affect fuel efficiency, such as:

• Type of aircraft and engine
• The length of flight, route flown and air traffic control restrictions
• The configuration of the aeroplane, the number of passengers and amount of cargo carried
• The weather

Determining which flight is best for the environment

This is a difficult question to answer as there are many factors involved. However, there are some general principles you can use when choosing a flight such as selecting airlines with modern (i.e. more efficient) aircraft.

The CAA continues to consider consumer’s interest in and access to information on aviation’s environmental impacts when they book flights. You can find more details about this work and read our research on this topic in the page on the Environmental Information pages.

What rules must airlines follow?

Rules and environmental standards vary from airport to airport. Airlines will have to meet the required standards to operate at that airport. If they don't, they may have to pay higher environmental landing charges, or the airport might restrict the number of flights they are allowed to make.

Some airlines are legally obliged to report their emissions. These are:

• those that fly on routes between European airports have to report their emissions under the Emissions Trading System
• those that are listed companies have to report their emissions under the Companies Act 2006 (Strategic and Directors’ Reports) Regulations 2013.

How can airlines reduce their environmental impact?

There are lots of ways that airlines can reduce the environmental impact of their operations.

These can include:

Noise

• investing in quieter aircraft
• using their quietest aircraft at airports where there are more people affected by noise
• sticking to operational procedures that reduce the noise impact.

Climate Change

• purchasing more fuel-efficient aircraft when replacing old aircraft
• ensuring that load factors are maximised so that emissions per passenger or tonne of freight carried are lowered
• developing the use of next generation biofuels
• finding ways to reduce unnecessary aircraft weight.

Air Quality

• on arrival - switch off main engines and limit use of aircraft auxiliary power units where possible.
• use fixed electrical ground power and preconditioned air if available at airports or ground power units.
• conversely, on departure delay switching on main engines until ready for push-back.

The industry body Sustainable Aviation highlights what airlines are doing to implement these measures in practice.