Mega-fires have occurred in Australia during the 2019/2020 bushfire season, leading to enhanced concentrations of many tropospheric pollutants. Here we report on a fire plume with unusually high and persistent HONO levels that we could tracked during one day at free tropospheric levels over the Tasman Sea on 4 January 2020 using IASI and CrIS satellite observations. HONO concentrations up to about 8 ppb were retrieved during nighttime. Persistent HONO concentrations (>1ppb) were still observed at sunrise. Model simulations suggest a significant contribution of primary fire emissions and heterogeneous photo-induced reactions to explain the observed concentrations. However, many uncertainties and unknowns remain in the plume aerosol load and in the chemical processes which may explain the model inability to reproduce HONO concentrations at sunrise.