Estimating nonvolatile particulate matter (nvPM)—or black carbon—emissions during an aircraft mission is extremely challenging because of the lack of reliable data in flight. For this reason, a detailed study has been undertaken to estimate in-flight emissions from data measured on the ground during engine certification. Aircraft engine emissions certification is based on the “Landing and Take-Off” (LTO) cycle developed by the Committee on Aviation Environmental Protection (CAEP) of the International Civil Aviation Organization (ICAO). It represents operations below 3000 ft. The aim of this regulation is to control and reduce pollutant emissions in the vicinity of the airport. Carbon monoxide (CO), unburnt hydrocarbon (UHC), and nitrogen oxides (NOx) have been regulated using the LTO cycle by different international standards for four decades. New certification standards on nvPM have been introduced recently. The first one, put in place in CAEP10, regulates the peak nvPM mass concentration. It has been in effect since 2020. The second set established in CAEP11 regulates the nvPM mass and number of emissions on the LTO cycle and it becomes effective in 2023. With these regulations, manufacturers are now reporting nvPM emissions data publicly. All emissions data of in-production engines, and some legacy engines, are available in the engine emissions data bank (EEDB), downloadable from the European Union Aviation Safety Agency (EASA) website. Methodologies have been proposed to estimate emissions at altitude and calculate total mission emissions for NOx, i.e., the “Boeing Fuel Flow Method” or the “DLR Döpelheuer and Lecht” methodology, which are only relying on these publicly available data from the EEDB. In the following, a new methodology for estimating nvPM emissions at altitude is proposed. The methodology was developed and validated in the framework of the CAEP technical working groups. It comprises four dedicated steps. In the present article, the different steps are explained and validation data is provided as applicable. Examples of in-production engines are analyzed, discussed, and compared against the full methodology using proprietary engine performance and emissions certification data. Following the proposed methodology, total nvPM mass and number of mission emissions can be estimated and used for emissions inventories and evaluation of climate impacts.