Multilayer film flow down an inclined plane in the presence of an insoluble surfactant is investigated with particular emphasis on determining flow stability and investigating the possibility of travelling wave solutions. The investigation is conducted for two or three layers under conditions of Stokes flow and, separately, on the basis of a long-wave assumption. A normal mode linear stability analysis for Stokes flow shows that adding surfactant to one of the film surfaces can destabilise an otherwise stable flow configuration. For the long-wave system, periodic travelling-wave branches are detected and traced, revealing solutions with pulse-like solitary waves on each film surface travelling in phase with each other, travelling waves with capillary ridge structures, and solutions with two of the film surfaces almost in contact. Time-periodic travelling wave solutions are also found. The stability of the travelling waves is determined by solving initial value problems and by computing eigenvalue spectra. Boundary element simulations for Stokes flow confirm the existence of travelling waves outside of the longwave regime.