As commercial entities, airports offer discounts, typically on landing fees and other aeronautical charges. In regulated environments they generally have to keep the discounts accessible to all, but access can be structured in a way that just happens to favour some carriers over others. Quite often there will be incentives to encourage new users and/or the development of new routes, these might take the form of "marketing support" - covering a wider range of subsidies less visible than discounts to aeronautical charges.