Originally Posted by findark

Stopover in SYD is perfectly allowed on the AA fare.

The gateway means the first transfer point in Area 3 outbound, or the last transfer point in Area 3 inbound. So -TYO-SYD- is not eligible but -LAX-SYD- is.

However, this is a mileage fare and not a routed fare, so you will get HIP checked and you will not like the resulting price. People stopping over in Japan are using the JL fare, which exempts Japan from HIP checks.