In the present work is made an overview of the use of hydrogen in aviation, the modifications needed to convert a conventional gas turbine to use hydrogen and a CFD simulation of an existent gas turbine burning hydrogen. The CFD simulation was done in a CFM56-3 combustor burning Jet A (as a reference standard) and hydrogen, with the intention of evaluate the viability of conversion of existent gas turbines to hydrogen, in a combustion point of view, by analyzing the emissions through ICAO's LTO cycle while burning this fuel. ANSYS Fluent 2020R2 was the software used to perform the numerical study. The RSM was the viscous model used. Only the NOx emissions were assessed as pollutant once the hydrogen combustion products are reduced to water vapor and NOx. These emissions were evaluated through a detailed mechanism and the NOx model available on ANSYS to get a better concordance with the ICAO's values. During this study, several sensibility studies were carried out for hydrogen burn, for instance, the analysis of the air flow with/without swirl in the primary zone and different inlet pressure and temperature for fuel.