Aircraft produce significant environmental effects. To address this problem, the European Commission established Clean Sky, an enormous project with the ambitious target of reducing aircraft emissions by 11 % by 2025. The 'Contribution of airlines for the reduction of industry nuisances and gases' (CARING) project was part of the Clean Sky programme. The nine-member CARING consortium ran from January 2010 to December 2011. Project researchers studied how airlines presently deal with environmental constraints and how they would in the future. CARING aimed to document the trajectories that airlines really fly and to determine their environmental impact. The consortium also aimed to understand the effect of environmental regulations on airlines, and to build an economic model of airlines and environmental effects. To achieve these goals, the project used flight recorder data obtained from thousands of flights from nine aircraft types. The six studied airlines represented regional, budget, charter and long-haul types. The resulting analysis revealed differences in the trajectories, and illustrated the reasons for certain trajectory choices. The analysis showed potential for improvements to trajectories and operating procedures, while remaining realistic. CARING also studied noise and pollution constraints on aircraft worldwide, illustrating their financial and other effects on airlines. Subsequently, the project surveyed hundreds of airlines in terms of how they adapt to the regulations. As a result, CARING developed several scenarios exploring economic conditions. The scenarios included various costs to airlines and airline response, and made predictions about the likely evolution of regulations. Project studies served as input to a global economic model, showing how airlines respond to constraints (particularly the EU's Emissions Trading Scheme). The circumstances studied included monopoly, duopoly and fully competitive environments. The models were compared against the above scenarios, showing whether environmental constraints would benefit a given airline. The project's overall conclusion was that low-pollution aircraft give airlines a competitive advantage while also benefiting the environment. CARING data has resulted in documented business reasons for airlines to fly environmentally friendly aircraft. The economic model will facilitate the end encourage adoption of green technologies by airlines.