Are there any deserted islands in the world which dont fall under any government which may or may not appear on a political map of the world? If so, can chartering a private jet from west africa to the south pacific or anywhere else be feasible?
Gilligans island
>Are there any deserted islands in the world which dont fall under any government
In a word, no.
There are plenty of 'desert' islands (i.e. with no human inhabitants) but being deserted is not the same as being unclaimed territory.
https://en.wikipedia.org/wiki/Desert_island
There are also plenty of private islands you can buy if you have the money to do so....but even privately-owned islands are governed by a country e.g. Necker in the British Virgin Islands, Cayo Espanto in Belize, Lundy Island in the UK...........
I doubt your very expensive charter jet will be happy to land on a beach without a proper airstrip.
And as Leics has said, all the islands are claimed by governments. The closest there are to unclaimed lands are disputed no-man's-lands between countries, which may not be under government control.
I have had some survival training in the military. But I would not want to live on a deserted island. I like running water, flush toilets, electricity for air conditioning, easy access to hospitals, TV, internet, etc. Also bring cases of bug spray, sun block and probably some sort of personal protection.
If you can afford to charter a jet you can find some private out of the way place to stay in a small town and have some basic comforts. Criminals seem to find a way to fade into the background without discovery without "roughing it!"
There are some survivalist type programs you can look into too. (Google type search will come up with some suggestions.)
A search for "private islands for sale" and "want to buy a deserted island" came up with more info than I expected.
[ Edit: Edited on 29 Aug 2021, 10:23 GMT by karazyal ]
Why not rent a private island off the coast of Honduras for $175 USD per night? 
The accommodation looks quite comfy and the kitchen even comes with two refrigerators. For a very economical price you can try out island life for a few days and see how it goes! 
I'm not sure being on an unclaimed island would be all that good. It would basically mean you are at the whims of international law which isn't really that well enforced
. Just look at the South China Sea disputes, it is a pretty volatile situation and there is no recourse or protection when one side is shooting at the other because technically it is lawless. Much better to be under some umbrella of a government.