Based on its well-known merits ammonia has been gaining special attention as a potential renewable energy carrier which can be replaced in power generation systems. Considering its low flame speed as one of the main challenges of combusting ammonia, flame stability is experimentally investigated. Focus is on premixed ammonia-hydrogen-air flames with high mixture fractions of ammonia (60-90% by volume) under standard temperature and pressure conditions. Silicon-carbide (SiC) porous blocks are used for stabilizing flame in a wide range of conditions. Upper and lower stability criteria are established for various mixture compositions. Also, combustion completeness is evaluated by analyzing measured and predicted temperature. The remarkable capability of the porous medium burners to efficiently operate at very high fractions of ammonia in a wide range of equivalence ratios provides a new achievability in more efficient combustion in power generation applications. (C) 2017 The Authors. Published by Elsevier Ltd.