Out in a week or two, the 0.52b release will add a whole bunch of weather effects (with the option to keep them disabled if you are playing on a less powerful machine)
New objects are provided in the shape of the cooling towers, which based on their size and model complexity are either easy/medium/hard to dive into and out the bottom.
The car is an experimental feature to see if people might want this as a more refined option later.
Finally, I kept getting complaints that the plane is too twitchy, so I've amended to default rates to it's nice and gentle now.
The weather and car are only available in the single player version of the game, the cooling towers will be in the online version of the map for this release.