St Martin airport in Grand Case is a regional airport deserving directly only 3 destinations : Martinique, Guadeloupe and St Barts. From Pointe a Pitre in Guadeloupe or Fort de France in Martinique you can have international destinations to the USA, to France, to other Caribbean islands. St Martin airport in Grand Case is small airport as you can see on the pictures on the right. But It can receive private jet flights.
So for an international flight from St Martin you need to go to the Dutch side in Maho at the St Maarten airport Princess Juliana.