Yes, you can connect to an FTP server.
As Air SIMs are assigned a private IP address behind a NAT, ensure that you connect to your FTP server in passive (PASV) mode. Active FTP mode is not supported.
Please note: The standard FTP protocol is not encrypted, and connections from your device to an FTP server over the Internet can be eavesdropped. Ensure that your data is appropriately encrypted before sending over FTP.