To investigate the thermal safety behavior of lithium-ion batteries during the air transportation process, the batteries with different states of charge (SOC) are heated by heating coil under low pressure. The thermal runaway (TR) behaviors of the batteries are investigated by analyzing the differences in TR phenomenon, temperature, time, and voltage. The results show that the voltage drop time is earlier than the gas release time for all the batteries. The increase in the SOC shortens the voltage drop and TR time, and increases the TR temperature and intensity of the batteries under all pressures. In addition, the reduction of pressure leads to the delay of voltage drop time, the reduction of TR intensity and temperature, and the U-shaped change of TR time. The influence of SOC on the TR behavior is attributed to the difference of lithium content in the anode which leads to the difference in the energy state and stability of the battery. The difference in TR behavior under different pressures is due to the difference in oxygen content and heat transfer efficiency, which affects the ignition time and combustion behavior of the battery.