The boeing 747 has a cruising altitude of 45,000 feet and cruising speed of 275 m/s. at this elevation, the temperature and pressure according to the us standard atmosphere (air properties as a function of altitude) are 220k and 1.8x104 pa, respectively. the engines are steady state devices that can be modeled using the 1st law of thermodynamics with air (ideal gas) as the working fluid undergoing several processes.