Operational Experience: Airlines may require a minimum number of years of operational experience to ensure that the airline has the necessary expertise and knowledge in the industry.

Fleet Requirements: Airlines may have specific requirements for the type, size, and condition of aircraft in their fleet. This ensures that the airline's fleet meets safety and operational standards.

Financial Performance: Airlines may evaluate the financial performance of prospective partners or operators to ensure they have a stable financial foundation and are capable of meeting financial obligations.

Operational Capacity: Airlines should have the necessary infrastructure, resources, and capabilities to operate flights. This includes having a fleet of aircraft, trained flight crew and ground staff, maintenance facilities, and adequate operational support systems.

Customer Service Standards: Airlines may be expected to maintain certain customer service standards, including timely and accurate information provision, fair and transparent pricing, handling customer complaints, and meeting accessibility requirements.

It's important to note that these eligibility criteria can vary depending on the country and the type of airline operation (domestic, international, charter, etc.). Each airline will have its own specific requirements and processes for evaluating and selecting operators or partners.

Licenses and Certifications: Airlines typically need to obtain and maintain various licenses and certifications to operate. This may include an Air Operator's Certificate (AOC) or equivalent, which demonstrates compliance with regulatory requirements and authorizes the airline to provide commercial air transportation.

Compliance with Regulations: Airlines must adhere to local and international aviation regulations. This includes compliance with safety, security, customs, immigration, and labor laws. They may need to demonstrate a commitment to regulatory compliance and have processes in place to ensure ongoing adherence.

Safety Requirements: Airlines must meet and maintain specific safety standards set by the relevant aviation authorities. This includes compliance with safety regulations, proper maintenance of aircraft, and adherence to operational procedures.

Financial Stability: Airlines are often required to demonstrate financial stability and viability to ensure they can sustain operations. This may involve meeting certain financial benchmarks, having adequate insurance coverage, and providing financial statements or proof of funds.