Originally Posted by
Sam Drucker
I seem to recall this issue from long ago . . .
Johannesburg airport has an elevation of around 5,700 feet. No problems getting there, but the elevation reduces aircraft performance at take off, and airlines often can't load up with enough fuel (too heavy) to make it back to North American destinations. At least, not the combination of fuel, passengers, and freight they might need to make for a profitable flight.
It's often not that the aircraft couldn't load up with the required fuel and physically takeoff normally even under those conditions but due to having to account for single-engine climb performance in the event of engine failure during takeoff/climb at hot/high altitude conditions and reduced engine performance at hot/high altitude conditions, this often drives the lim-fac at hot/high altitude airfields. Airports like SLC and PHX have had issues and seen load restrictions during the hottest part of the day, even for shorter domestic routes due to limits driven by single engine climb performance.