Notes about the DA4 file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The DA4 file type is primarily associated with 'SeeYou' by Naviter. SeeYou is a planning and analysis tool for glider pilots. It is designed for the desktop and notebook PCs.