Thanks guys. Chris's photo shows everything there nicely, including:

- the EICAS message (based on Jet-A temperatures)
- the TAT (displayed in top left corner) equal to the fuel temperature (bottom right corner, coloured amber due to the temperature)
- a relatively low SAT (Static Air Temperature, equivalent to OAT, or just plain ol' air temperature, excluding any friction effects)

Mont, yeah it'll certainly be a factor on those flights, although probably more so on the EZE-SYD sector, where flights would traditionally be routed into the deep south latitudes to avoid the strong westerly jetstreams around 30-40 degrees south. Conversely, eastbound flights will often take advantage of these jetstreams and so take a fairly northerly route. On more than one occasion I've flown JNB-SYD along the rhumb line track (basically a steady course along 30 deg S), which took us over PER and ADL, and entailed a steady tailwind in the range 100-150kts the whole time!

Our Flight Dispatchers monitor predicted OATs for all JNB (and EZE) flights, and where the aeroplane's environmental envelope or fuel temp limits are likely to be exceeded, will usually provide for a more northerly routing. These flights are now also monitored for solar radiation, and re-routed during a major solar event.

Thanks for that Chris, I always just assumed CRZ would be selected but remaining on CLB for the reason you stated makes perfect sense.