What is the main reason for having reserve engines?

The main reason for having reserve engines is to accommodate engine removals without keeping aircraft on hold. In the aviation industry, aircraft availability is crucial for maintaining flight schedules and operational efficiency. When an engine needs maintenance or repair, having a reserve engine allows the aircraft to continue operating while the primary engine is out of service. This capability minimizes downtime and ensures that airlines can adhere to their timetables, meet customer demands, and avoid costly flight cancellations.

While reducing operational costs and ensuring efficient maintenance schedules are important in overall aircraft management, they are not the primary reason for having reserve engines. The enhancement of aircraft resale value may be a potential benefit, but it does not directly relate to the operational necessity that reserve engines fulfill. The focus of reserve engines is primarily on maintaining continuous operation and minimizing the impact of engine maintenance on aircraft availability.