In this paper, numerical simulation is performed to investigate the effects of micro air jets on mixing of the micro hydrogen jet in a transverse supersonic flow. The fundamental flow feature of the interaction between an array of fuel and air jets is investigated in a Mach 4.0 crossflow with a fuel global equivalence ratio of 0.5. Parametric studies were conducted on the various air jet conditions by using the Reynolds-averaged Navier Stokes equations with Menter's Shear Stress Transport (SST) turbulence model. Numerical study of eight streamwise transverse sonic fuel and air jets in a fully turbulent supersonic flow revealed an extremely complex feature of fuel and air jet interaction. The results present various flow features depending upon the number and mass flow rate of micro air jets. These flow features were found to have significant effects on the mixing of hydrogen jets. Results also show a different flow structure as air jet is presented in the downstream of each fuel jet. According to the obtained results, mixing rate is low in micro fuel jets without air jets. When the air jets are injected in the downstream of each fuel jet, the mixing of the hydrogen jet significantly increases (more than 60%) in the downstream. As the number of air jets is increased, the mixing performance of the fuel jet is increased more than 150%. Therefore, an enhanced mixing zone is obtained in downstream of the injection slots which leads to flame-holding. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.