Thansk Pudding Guy but with due respects to your chocolate pudding efforts I've just discovered that there is a way to get the sixth airline. I'm still eager to hear about other alternatives though.
It appears that you can fly on Avianca or Sam from San Jose to a little known Island called San Andres Island which is part of Colombia but off the east coast of Central America. It looks pretty peaceful and seems like a nice way to pick up that sixth airline. Has anyone been there? I wonder what it costs to fly there?
Here's the link
http://www.sanandres.net/english/travel.shtml
cheers Peter
cheers