In Rayleigh-Benard Convection (RBC), the working medium is confined between a cold plate at the top and a hot plate at the bottom. Due to temperature difference, a buoyancy driven flow starts developing which are complex and rich in details. Numerical analysis are widely carried out with Oberbeck-Boussinesq (OB) approximation for studying the convection patterns in different types geometries. The OB assumes a constant fluid properties except accounts the linear density variation with temperature in buoyancy term of momentum equation. In order to have a closer prediction of natural convection with experiment, the NOB effect is accounted in the numerical simulations. Two-dimensional Direct Numerical Simulation (DNS) of Rayleigh-Benard Convection of Jet-A fluid (Pr = 19.17) is performed in a square cavity. The Rayleigh number of this study are 10^6 and 10^7 with a temperature difference of 40K between hot and cold plates to account for non-Oberbeck-Boussinesq (NOB) effect. The Jet-A fluid, has higher viscosity and lower thermal conductivity compared to water and the Prandtl number is approximately 4.4 times higher than water at mean temperature of 40 deg C. The fluid properties of the working fluid are defined as a polynomial function of temperature. The OB approximation predicts flow reversals in the square domain for fluid Prandtl number (Pr) ranges from 1 to 10. This study is an extension of RBC for flow reversals beyond Pr = 10. The NOB code is validated with the literature data. The different statistical parameters both in the wall and bulk regions are documented. The Boundary layer thicknesses, the Centre line temperature, Flow reversals and the Proper Orthogonal Decomposition (POD) modes are investigated. We report the standard and cessation type flow reversals for the Jet-A fluid with Prandtl number of around 19 .The power spectral density (PSD) of velocity follows the Bolgiano-Obukhov (BO) scaling.