Shutdown options missing?

Checking web man pages there are at least two versions of the shutdown flags. RHEL lists -trhHPcK. but is mssing "akncfF". In particular I really like the "f" option to skip fsck on reboot. But, "f" is not listed in the RHEL man page for the shutdown command. Is it undocumented in RHEL, or is it missing? Thoughts anyone?