This paper is the result of a Master Thesis project performed at Saab AB. The main goal of the project was to design and implement a discrete time L 1 adaptive backup controller in pitch to increase performance for an agile fighter aircraft. A lateral controller was also developed as a secondary goal. A discrete time version of the Modified Piecewise Constant L 1 adaptive control formulation was implemented. Results have shown that augmenting a state-feedback controller with an L 1 adaptive controller increases robustness in the whole flying envelope, with satisfactory flying qualities. A switching scheme between two L 1 controllers based on the extension of the landing gear was used to improve the controller performance throughout the whole envelope. The implemented controllers were flown in a simulator with a nonlinear generic fighter aircraft model with promising results.