Abstract: This study aims to investigate the influence of thermal aging on the combustion behavior and fire hazard characteristics of PTFE-insulated aviation cables. Accelerated thermal aging was conducted at 200 °C for 10 days, and the variations in ignition behavior, heat release, mass loss, smoke production, and microstructural characteristics of the cables before and after aging were systematically analyzed using ignition tests, cone calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy. The results show that thermal aging significantly affects the fire performance of aviation cables. After aging, the ignition temperature decreased from 558.4 °C to 535.8 °C, while the maximum temperature above the flame increased from 731.3 °C to 829.9 °C. The time to ignition was shortened by 12%–25%, and the theoretical critical heat flux decreased from 42.75 kW·m⁻² to 40.98 kW·m⁻², indicating a reduction in ignition resistance. Under an external heat flux of 50 kW m⁻², the peak heat release rate increased from 30.12 kW·m⁻² to 35.52 kW·m⁻², with an increase of 17.69%. Meanwhile, the peak smoke production rate increased from 0.0151 m²·s⁻¹ to 0.0162 m²·s⁻¹ at 70 kW·m⁻², accompanied by an earlier release of CO₂. FTIR and SEM results further reveal that thermal aging weakens the characteristic peaks associated with CF₂ groups and induces cracks and pores on the insulation surface. These findings demonstrate that thermal aging deteriorates the chemical structure and surface integrity of PTFE insulation, thereby reducing the thermal stability and flame-retardant performance of aviation cables and increasing their fire hazard under external thermal radiation. This work provides experimental evidence for aging assessment and fire safety evaluation of aviation cables.