If it is really important you may be able to look at having a section of your ticket maybe landing in Miami and departing from Mexico City. I had a quick look on a discount airline booking site and it doesn't appear that any cheap flights between America, Cuba and Mexico exist (at least not showing on that site). A charter flight that goes from Cancun-Havana-Cancun costs $345US return including tax or if you did Miami-Havana-Cancun it'd be over $600US using the same charter company. So you'd sure be paying a lot more.
[ Edit: Edited on Apr 13, 2007, at 4:09 AM by aharrold45 ]
Cheers aharrold! I think I have found a solution though - havn't checked with a travel agent yet, but it looks like it would be available on the milage based oneworld ticket. Basically travel overland from Miami to Los Angeles, and then fly back to Cuba (as a sudden change of plan so that I can still use American Airlines up until that point). I can then get a flight straight from Cuba back to England, so although I would be backtracking, it wouldn't be a massive de-tour, and I would still be able to do Papeete and Easter Island.
Thanks for everyone's help,
You should try using this site to determine if your ticket is going to be alright http://gc.kls2.com/
That has a program which will determine your mileage and things (to a fairly close amount but not exactly as the airlines will tell you). When I used it for my oneworld RTW ticket, it even told me which legs were going to be invalid. To use it though you'd need to use the 3 letter airport codes in the box which says "paths", or if you type in the names you'll need to select from the airport list that will show for each one you type. When you have an overland section for the flights you put a , between then arrival airport and departure airport. So for London-Hong Kong-Sydney-Los Angeles overland to New York and then flight to London it would be LHR-HKG-SYD-LAX,JFK-LHR If you don't put the , in between and instead put a - it will be calculating your mileage wrong and probably tell you that you have mistakes with the ticket. After you've done that you click "display map" and it will show you the flight paths and the mileage etc that you'll need to be able to tell if you have got too many miles for a mileage based ticket, because any overland section also adds to your miles on the ticket even though you aren't flying.
According to the most recent travel planning thing for the Oneworld fare, no flight exists between Los Angeles and Cuba at all. The closest thing that exists anymore is Cancun-Havana and then from Havana-Madrid(or Barcelona)-London. Even the Miami-Havana flight that was about when I got my ticket last year isn't available anymore according to the file I downloaded off the oneworld site. Goodluck with it.