The invention relates to methods and apparatus for altering the software of engine controllers. The method comprises determining a version of the current software in the engine controller, identifying one or more data blocks of upgraded software associated with the current software and replacing portions of the current software with the data blocks of upgraded software. The apparatus comprises an interface, a memory and a processor. The processor is configured to determine the version of the current software in the engine controller and replace one or more data blocks of the current software with one or more data blocks of upgraded software stored in the memory.