Question 52915
I don't know if this is the best answer but I can get 500 across the desert.
Take 1000 bananas to the 250 mile mark. Drop off 500 and go back to the start.
Again take 1000 bananas to the 250 mile mark. Drop off 500 and go back to the start.
Load the last 1000 bananas and travel to the 250 mile mark. You now have 1750 bananas at this position.
Take 1000 bananas to the 500 mile mark. Drop off 500 and go back to the 250 mile mark.
Take the 750 bananas to the 500 mile mark. You now have a total of 1000 bananas at this point.
Load all the bananas and walk to the other side of the desert. You will use up 500 of the bananas so you will still have 500 left.
Presumably the reference to a 1000 mile wide desert is so that the camel has to cross the desert rather than walk around it.