There is a general trend toward user reprogrammability in EW equipment, as exemplified by the ARL-74 Radar Warning Receive and ALQ-165 ASPJ jammer. EW trainers are likewise moving toward greater reprogrammability by the user. EW trainers have large data bases for simulated threats and ownship equipment. Reprogramming enables the user to keep the trainer current with updated threat data and with modified versions of EW equipment employed in the trainer. EW trainers are reprogrammed by changing input data. Data can be performance parameters or control data that trigger various functions in the trainer software. Off-line data editors ease the task of changing data. A number of problems remain in the generation and use of reprogramming facilities. The first is the definition of user requirements. Second, the user must collect and digest data to make updates. Finally, the user must contend with configuration control problems if each user site can reprogram the trainers separately.