To reduce climate impact, switching to carbon-free electrofuels is an interesting option to reduce greenhouse gas emissions from electricity generation. The emission of other pollutants than CO₂, such as nitrogen oxides (NO_x), however, remains a concern. This research focuses on investigating the impact of transient phases, such as start-up and load change, on the NO_x emissions expected from the rich combustion of mixtures of hydrogen and ammonia in gas turbines. Stochastic processes account for the inherent variability and uncertainty on the transient trajectories. The trajectories are simulated using a one-dimensional premixed flame model built in Cantera to compute the levels of pollutant formations, among others. The results indicate significant variations in the equivalence ratio, leading to high NO_x emission peaks. The study concludes that the impact of the uncertainties related to the transient trajectories on the NO_x emissions is low compared to the overall variations of the equivalence ratio, although they can accentuate observed peaks.