This study establishes a staged airworthiness compliance verification methodology for turbofan engine endurance testing with triple red line (TRL) classification, focusing on minimizing configuration modifications while preserving regulatory compliance. Through systematic analysis of airworthiness requirements and in-service operational scenarios, a tiered verification scheme is developed for engines operating in non-TRL configurations. Numerical comparisons of creep damage in turbine blade stress-concentration zones under TRL conditions versus graded verification scenarios confirm that the proposed method maintains the rigor of airworthiness assessment criteria. The methodology provides an engineering-viable approach for pre-certification testing, offering direct compliance verification with airworthiness regulations when full TRL conditions are unattainable.