A multi-national research team from the National Institute for Environmental Studies, Zurich University of Applied Sciences, Tokyo Metropolitan University, and other institutions (hereinafter referred to as “our research team”) conducted emission tests on aircraft engines and examined the shapes and internal structures of the exhaust particles with high-resolution transmission electron microscopy. Our research team identified novel onion-like (multiple concentric spherical crystal layered) particles and amorphous (non-crystalline) particles, in addition to the well-known soot in the aircraft engine exhausts. The exhaust particles were typically very small (approximately 10–20 nm in diameter) and single spherical particles. Although the detailed physicochemical properties of the onion-like particles are currently unknown, their behaviors in the atmosphere and in the body may be different from other particles. Therefore, further research is required to assess their potential impacts on climate and health. The related research paper has been published in ACS ES&T Air, a journal in the field of atmospheric sciences, by the American Chemical Society (ACS), on 8 April 2025.