Cassius Bright went aboard the airliner, The Linde, at the landing port to go reach the Erebonian Empire. This was the same airliner that went missing and got captured by the Capuas, and it would propel Estelle and Joshua's journey around the kingdom.
Later, Estelle, Joshua, and Scherazard are looking for Josette for stealing the septium crystal and they go to the landing port to find any clues to where she went or if she's still at the port. When they talked to Skip about that, he noted that no one in a school outfit could've come through the port today which basically knocks the idea that Josette is leaving by airliner out the question. Fortunately, the Servais Leaf Estelle found would lead them to Josette's whereabouts in Mistwald Forest.
The landing port is set in the City of Rolent in the region of Rolent in Liberl Kingdom. The port is straight north of the city, and there is a bottom level for all the workers and an upper level for all the passengers to exit and enter the airliners that are in the port that the time. The bottom floor is full of cargo and warehouses to hold everybody's items together.