Civil aviation is now central to global climate discussions, yet cross-national disparities in emissions and carbon reduction burdens remain underexplored. This study constructs the first harmonized, multi-pollutant global aviation emissions inventory from 1996 to 2023, integrating all scheduled flights worldwide. Systematic comparisons reveal persistent inequalities: while aggregate emissions have surged, especially in emerging economies, per capita emissions remain concentrated in high-income countries. Although efficiency gains from rapid fleet modernization in developing countries are notable, they lag behind soaring demand. Decomposition shows domestic aviation growth is the chief driver in emerging markets, while international flights dominate new emissions in advanced economies. Carbon reduction costs under the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) indicate mounting burdens for developing countries, highlighting critical challenges for climate justice. Our findings highlight the necessity for differentiated, equity-oriented policies and targeted support to reconcile aviation growth with global decarbonization and fairness goals.