The findings suggest a potential vulnerability in America’s fifth-generation stealth technology and mark a significant leap in China’s pursuit of anti-access/area denial capabilities.

The team found that while the jet’s radar-absorbing coating and exterior cooled to an average 281 degrees Kelvin (7.85 degrees Celsius or 46 Fahrenheit), effectively masking it from traditional detection, its engine exhaust plume, which reaches nearly 1,000 Kelvin, emitted mid-wave infrared radiation three orders of magnitude stronger than its airframe.

By focusing on the 2.8-4.3 micrometre wavelength range – where atmospheric interference is minimal – and deploying mercury-cadmium-telluride detectors and 300mm aperture telescopes, the unmanned airship hovering at 20km could spot an F-35’s rear thermal signature more than 1,800km away when the aircraft was viewed from the side or behind.

However, detection from the front remained limited to 350km because of the stealth jet’s reduced forward heat profile.