According to IBM's AIX documentation for ftpd, there is a
-ff flag which:
Disables checking for both a privileged port and an IP address that matches the one used for the control connection when the client requests the server to connect back to a specific client port. Using this flag enables the client to request that the server send data to an alternate host or interface. By default, ftpd does not allow this action as a security precaution.
This seems as though it would allow FXP, especially since according to Wikipedia:
Although FXP is often considered a distinct protocol, it is in fact merely an extension of the FTP protocol and is specified in RFC 959
If that is the case, FXP is disabled by default since the option is not specified in
inetd.conf. You can confirm by adding the flag and trying to initiate an FXP transfer. The transfer should only be allowed when the flag is in place.