Curfews
Areas suffering the impacts of noisy aircraft will often impose overnight curfews, greatly reducing the operational hours of an airline. Such a reduction in business impacts the profitability of an airline greatly.
Noise Complaints
Noise issues not only affect the lives of home owners in the area, but can lead to the regulation of airline operation, reducing profitability and damaging the reputation of a company.
Flight Diversions
Noisy aircraft may need to fly at a higher altitude or along a less direct flight path to reduce the consequences of the sound produced. This increases flight time and energy expenditure - increasing cost.
Noise Tax
Taxes exist in certain areas which require aircraft operators to pay for the disturbance they produce as a result of noise. This outgoing cost decreases the profitability of an airline.