What is "Ferry Routing"?

1. Make valkiries in gunship plant.
2. Make whatever light units you want.
3. Place a ferry route.
4. Direct the transports and ground units to stand in the circle.
4 ...?
5. Profit!

You need some transports beforehand. Valkyries work best. Surfboard probably works but it is a terrible unit that needs to die in a fire, I don't recommend using it regardless.

You choose the ferry route "command" (not really a command, it's available even without any units selected) and click a source and a destination point.

Now, any units' move orders into the source circle are handled differently. On arrival they get a Wait command and an idle transport moves them to the destination, whereupon they continue with their queue. If no transport is available they patiently wait.

One use case is to speed up arrival from factory onto the frontline. It is unused because facs are dirt cheap so it's better to make a new one on the front instead unless you have spare transports from elsewhere.

The other use case would be to create an automated bridge of sorts between impassable areas. It is unused because on maps with such areas (eg. water) there is absolutely no reason not to use the fac that can traverse it by itself (eg. amph).

Surfboard might have uses (floating Scallops?) if its pricepoint was closer to Valkyrie. Valkyrie feels a little bit cheap at 80 but it would be very bad at 220. If that were done Surfboard could afford to have a little less HP, 1200 feels like overkill.

As far as I know the Ferry command is not deprecated, but very few people are comfortable enough with it and Transports in general to put its narrow use cases to good effect. Transports in general are mostly only used for cheeses like skuttle drop, double scallop drop, or comnap, except by the (very) few players who like to drop in mid-late game.