This dataset contains isotopic sampling of methane taken on board the British Antarctic Survey (BAS) twin-otter aircraft during a flight campaign over the Llanos de Moxos wetland near Trinidad, Bolivia in 2019 and supporting model simulations for the Methane Observations and Yearly Assessments (MOYA) project. Air samples were collected in tedlar bags during flights over the region and subsequently analysed at the Greenhouse Gas Laboratory, Royal Holloway University (RHUL). These are supported with data from a nested GEOS-Chem model simulation at 0.25° x 0.3125° which was used to map the relationship between emissions and aircraft measurements in a regional domain bounded by 24 - 0 °S and 75 – 55 °W. In addition, a footprint of the air source was simulated for each minute of aircraft sampling to capture using the Met Office NAME model at of 0.14° × 0.09° and temporal resolution of 3 hourly.