Many simulator processes and algorithms have been implemented in FORTRAN. Some examples are ocean models, aircraft avionics models, and sonar sensor models. As we begin writing training device software in Ada^R, it is important that we consider reusing existing FORTRAN code. This is particularly true for FORTRAN based trainers undergoing major software modifications. Various techniques for interfacing Ada and FORTRAN designs are investigated. Benchmarks are presented comparing an all FORTRAN or all Ada implementation to a combined FORTRAN/Ada implementation. Problems concerned with calling FORTRAN subroutines from Ada procedures and tasks and vice versa are explored. Differences in arithmetic types between the two languages are also explored. Particular emphasis is placed on the effect that a combined Ada/FORTRAN implementation has on computer resources. This consideration is of major importance when modifying an existing trainer where spare time and memory may be very limited.