3D-FTP can automatically resume transferring if the connection is broken in the middle of the transfer for any reason. Resuming means that the file transfer continues from the exact position of the interruption, without the need to start over. This is especially handy when transferring big files or trying to transfer data to/from a very busy FTP Server over a bad connection.
Changing Resume Settings
If the file already exists, you can change Resume settings in Settings > General Settings > File Viewer tab > Action. Read more about resume settings here. The default settings are Resume on download and Ask User on upload.
NOTICE! The Resume function requires support from the FTP Server. So if the server you are connected to does not support Resume, 3D-FTP cannot resume the transfer; instead, the file must be transferred from the beginning if the connection is lost in the middle of the transfer. Fortunately, almost all FTP Servers now support the Resume function.