My RTW was issued last year : ....... IST-MAD-HAV, MEX-YVR-JFK-YYZ-HKG....

When the ticket was first issued, I don't think MX was an option yet. So I had a surface HAV-MEX. I was prepared to buy a separate MX ticket.

MEX-YVR was a JL flight. This has now been changed to a MX flight. So I thought, since MX is part of the team, I could now get a HAV-MEX segment included too.

So I called Qantas this evening and was told some rather strange information -
There would not have been any problems adding an additional MX ticket at this stage but because the segment involved Cuba, it was illegal! So I still have to purchase a separate bolt on ticket from HAV to MEX.

I'm really puzzled. My RTW was issued by Qantas. No AA flights involved. So I can get into Cuba via Europe but I can't get out from Cuba to MEX unless I have a separate ticket? Any idea what the rationale is?

I don't mind buying a one-way HAV-MEX as planned previously but I'm really curious to know why it is illegal to fly me out from HAV on the RTW ticket!

This is so confusing!