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Coal mining is a significant human-induced source of atmospheric methane (CH4) on a global scale, contributing notably to national emissions in coal-producing countries such as Australia. Australian mining operators use tiered, bottom-up methods aligned with IPCC guidelines and implemented under the National Greenhouse and Energy Reporting (NGER) scheme to estimate emissions from underground and surface mines. However, underground mine emissions have not been systematically validated by comparison with top-down atmospheric measurements, and surface mine emission factors lack empirical support. Studies have revealed significant discrepancies between top-down and bottom-up estimates at investigated surface mines, prompting concerns about the effectiveness of the current regulatory methods.In 2023, two independent airborne measurement strategies were used simultaneously by deploying two aircraft to quantify CH4 emission rates from coal mining in the Bowen Basin (Queensland, Australia) as part of the United Nations Environment Programme’s (UNEP) International Methane Emissions Observatory (IMEO) study. A total of 53 emission rate quantifications for 16 coal mines were achieved from the measurements collected within a 31-day campaign. Comparing these estimates with operator-based estimates from underground mines revealed no significant bias at the facility- and aggregated-level, with operator estimates being well within the uncertainties of the airborne estimates. However, a comparison with surface mines showed significant biases at both the facility- and aggregated-level, exceeding the uncertainties of the airborne estimates.Globally, these results add to growing evidence that Tier 3 approaches based on direct measurements are suitable for estimating fugitive CH₄ emission rates from underground mines. By contrast, the results from surface mines suggests that IPCC Tier 2 and 3 inventory methods (i.e. use of emission factors and potentially coal gas distribution models) for surface mining require careful implementation and independent verification.This poster will present and discuss the results of the measurements taken in the Bowen Basin.