A silly little calculation.

Total commercial hours flown in Australia in 2009 was very, very roughly 2 million.
http://www.bitre.gov.au/publications/26/Files/General%20Aviation%20Activity%202009.pdf

For the sake of this exercise I will assume they are all 767's, averaging 500 km's per hour, which means 1 billion kilometres are travelled. (To put this into perspective, some of them were balloons, and some were 747's. Did I mention this was going to be rough?)

It takes 1 acre to produce 328 gallons of ethanol. Say that translates to producing 300,000 litres of aviation fuel per square kilometre.
http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/question707.htm

767's use 15 tons of fuel for 1800 nautical miles. Fuel has a density of 0.8 Kg / litre, so for our purposes that equates to 0.2 km / litre. (What a coincidence. If it is carrying 100 people that puts it in the same km/litre/person ballpark as a single passenger car.)
http://www.pprune.org/tech-log/114922-767-300-fuel-consumption-t-o-dist.html

So it will require 1,000,000,000 / 0.2 / 300,000 which is roughly 16,000 square kilometres to produce that fuel.

For the sake of comparison, we have roughly 4,000 square kilometres of sugar cane planted now.

Rstuart, interesting calculation. I had seen something similar previously.
It appears that the aviation industry has now switched their interest
to algae. Not sure why but it might be because it can be made in a
chemical style plant and will not be seasonal. It could also because
there are not the same temperature problems.

However, while millions are thinking of putting their cars up on blocks
they would not be too happy watching the businessmen flying overhead.
It might just not be politically possible.
The big hope of course is natural gas but the capital expenditure may
well beyond the capability of the economy. The cost of fitting every
service station with NG pumps and need to supply them with fuel
either by tanker or pipeline is enormous.
These are the sort of things that the governments should have been
organising but they have left it too late.