The GOES-R PLT Southern Ontario Lightning Mapping Array (LMA) dataset consists of total lightning data measured from the Southern Ontario LMA (SOLMA) network during the GOES-R Post Launch Test (PLT) airborne science field campaign. The GOES-R PLT airborne science field campaign took place in support of the post-launch product validation of the Advanced Baseline Imager (ABI) and the Geostationary Lightning Mapper (GLM). The LMA measures the arrival time of radiation from a lightning discharge at multiple stations and locates the sources of radiation to produce a three-dimensional map of total lightning activity. These data files are available in compressed ASCII files and are available from April 1, 2017 through June 1, 2017.