In this paper we discuss the design and use of a fault tolerant MPI (FT-MPI) that handles process failures in a way beyond that of the original MPI static process model. FT-MPI allows the semantics and associated modes of failures to be explicitly controlled by an application via a modified functionality within the standard MPI 1.2 API. Given is an overview of the FT-MPI semantics, architecture design, example usage and sample applications. A short discussion is given on the consequences of designing a fault tolerant MPI both in terms of how such an implementation handles failures at multiple levels internally as well as how existing applications can use new features while still remaining within the MPI standard.