I understand your opinion, but Bukkit has simply not necessary - the API provides a great way to prevent a flymod. And we have the allow-flight flag from the vanilla-server in the settings-file to kick every user with flymod. But why it has to be hardcoded and without the feature to disabled it? And why the server only teleport to the ground? I personally think/hope it is a bug. But without a statement it could really be anything: a bug, a new feature or an failure - we don't know it.