Summary of the mass loss rates and their errors found in the LTE case compared to the expected mass loss rates from the theoretical studies of Fossati et al. (2018) and García Muñoz & Schneider (2019). Our finding shows that the KELT-9 b thermosphere probably undergoes a “Balmer-driven” expansion, that leads to a high escape rate. In this case, the total mass loss through the planetary life time (500 My) represents sim 0.05 M_Jup, which is sim 2% of the planet mass.