Fazenda Alto da Serra Airport (ICAO: SJN3) is a small private airstrip located in the municipality of Porto Nacional in the state of Tocantins, Brazil. It serves the agricultural estate (fazenda) for which it is named, providing general aviation access to a region where road infrastructure can be limited. The airport has no IATA code, reflecting its status as a private, non-commercial facility. It is typical of the many private farm airstrips found across Brazil's interior, supporting the agricultural and ranching operations of the Tocantins region.