Growing popularity of the mobile code requires to consider various aspects related to its security. In the aviation industry there is a case when additional information needs to be delivered to the pilot by uploading it from the ground station. It creates a need for a platform-independent solution and it raises a problem of the mobile code security as well. Organization of the security in the Base System (similar to extranets) as well as the security issues of the mobile code (or safelets for use in the aircrafts) delivered to the Remote Platform are discussed in the paper. Safelet implementation technologies and issues of code effectiveness and safety itself are discussed with Java and Juice/Oberon technologies been compared.