On-board avionics systems are proprietary and no standardisation is expected in the foreseeable future. The various microprocessors employed dramatically vary in their performance. Thus, for the additional information delivery to the pilot from the ground station, we need a platform independent solution. Concept of Dynamic Safety (CoDySa) has been developed during 1990-1996 primarily targeting improvement of aircraft safety. This paper presents further development of the CoDySa principles, namely ground-to-air communication architecture. Possibilities to upload safety-enhancing software components (safelets) are discussed together with scenarios of their use. Safelet implementation technologies are discussed. Java and Juice/Oberon have been compared. Issues such as code effectiveness and safety are emphasized. Juice/Oberon has been recognized as a better candidate for implementation of safelets.