Instability in Models Connected with Fluid Flows I presents chapters from world renowned specialists. The stability of mathematical models simulating physical processes is discussed in topics on control theory, first order linear and nonlinear equations, water waves, free boundary problems, large time asymptotics of solutions, shastic equations, Euler equations, Navier-Stokes equations, and other PDEs of fluid mechanics. Fields covered include: controllability and accessibility properties of the Navier- Stokes and Euler systems, nonlinear dynamics of particle-like wavepackets, attractors of nonautonomous Navier-Stokes systems, large amplitude monophase nonlinear geometric optics, existence results for 3D Navier-Stokes equations and smoothness results for 2D Boussinesq equations, instability of incompressible Euler equations, increased stability in the Cauchy problem for elliptic equations. Contributors include: Andrey Agrachev (Italy-Russia) and Andrey Sarychev (Italy); Maxim Arnold (Russia); Anatoli Babin (USA) and Alexander Figotin (USA); Vladimir Chepyzhov (Russia) and Mark Vishik (Russia); Christophe Cheverry (France); Efim Dinaburg (Russia) and Yakov Sinai (USA-Russia); Francois Golse (France), Alex Mahalov (USA), and Basil Nicolaenko (USA); Victor Isakov (USA)