Otabo is right. There are 15 routes and he lists the correct ones.
Actually, I would have accepted 16 as a correct answer as well. That is because technically there is another route (defined as X -> Y) from Matango to Kakkara Dessert (not Kakarra Village) but this is debatable. The unique flight to Kakkara Dessert is explained as a miscalculation by the cannon man later. However, in the German translation this route is labeled as Kakkara Dessert ("El Sandalar") instead of Kakkara Village ("El Oasis"). Here the cannon man intends the differing destination at this point of the story, saying he sends you right into the dessert before the flight starts.
Another side note:
-Water Palace/Gaia's Navel (after getting Spear) : The appearance of Gaia's Navel is changed for version 1.1 of the game. Here this route opens up at a later point of time, so you cannot skip Pandora early, thus making this route very hard to come across at all due to the fact it is disabled soon after.
Anyway ... Otabo is next.
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