The fifth International conference on Nonlinear Problems in Aviation and Aerospace was held at University of Timlsoara, Romania in June 2004. This proceedings publication includes keynote addresses, invited lectures and contributed papers presented at the conference. Mathematical problems in engineering and aerospace science have stimulated cooperation among scientists from several disciplines and developments in computer technology have led to solutions of mathematical problems. The publication includes papers on aeroacoustics, aerodynamics, computational fluid dynamics, air traffic control design, nonlinear filtering, atmospheric flight mechanics, propulsion and combustion, navigation, guidance, stability and control, neural networks, optimization, computer security and cryptography.