does latest Airport extreme support static routes?

Not sure what you mean by static routes.

The AirPort Extreme can be configured to connect to a modem or another router using a Static IP address.

In addition, if the AirPort Extreme is configured to act as a router for the network, the AirPort can assign Static IP addresses to connected clients in the 10.0.x.x, 172.16.x.x, or 192.168.x.x ranges.

No, it does not support static routes.

Although Airport Extreme does not support static routes, I have found that if you are running OS X Server, and you put a static route on the server machine, then that static route is available to all machines that run through it (assuming that you are running the part of or all of the DHCP service on the server), or at least enough of the DHCP so the client machines are running through the server.

So, a machine that is on the 172.16.x.x subnet can access the main 10.0.x.x subnet, so long as the 172.16.x.x subnet was added to the server's routing table using the Terminal app and a command such as "route -nv add -net 172.16.10.0 10.0.0.2".

In this case, if you type in 172.16.10.2 it will route to 10.0.0.2.