Aeroelastic instabilities are an important factor in the design of modern high-speed, flexible aircraft. The current trend is toward the creative use of composites to delay these instabilities. To obtain an optimum design, an accurate as well as efficient model is required. As a first step towards this goal, aeroelastic analysis is carried out for a swept composite box beam, using a linear structural model and a linear 2-D unsteady aerodynamic theory. Structurally, the wing is modeled as a thin-walled composite box beam of rectangular cross section. Theodorsen’s theory is used to get the 2-D unsteady aerodynamic forces, which are integrated over the span. The flutter solution is obtained using the V-g method and divergence speeds are calculated by using a very low reduced frequency in the flutter analysis. The variation of critical speeds with composite ply layup is plotted for various sweep angles. These trends are compared with those available in literature.