Flying boat

The flying boat (飛行艇) is a multi-purpose surveillance vehicle developed by the nation of Hizuru some time between the years 852 and 854.

Uses
Hizuru's flying boat is the first known vehicle of its kind. As the name suggests, the flying boat can function as both a ship and an airplane depending on the users' needs, and the wings can retract for more accessible aquatic transport.

The flying boat is fueled by iceburst stone which is found in Paradis Island. While anyone with sufficient piloting skills can accomplish the flying boat's operation, this can only be managed after a thorough examination, preparation, and testing by a specialized team of engineers. The vessel's development for a flight can take half a day or longer, depending on the availability of necessary maintenance equipment.

War for Paradis arc
Shortly before the first meeting of the people of Hizuru and Paradis Island, Zeke Yeager meets with Hizuru ambassador Kiyomi Azumabito in secret, providing her family with a sample of iceburst stone to encourage an alliance between Hizuru and Eldia. By the year 854, Hizuru manages to fully realize the potential of the iceburst stone, integrating it as the primary fuel source for their newly developed flying boat. After Eren Yeager's raid on Liberio, Kiyomi returns to Paradis Island with the newly developed flying boat, intending on using the ship to view a small-scale rumbling from an aerial perspective. However, the subsequent Yeagerist uprising overturns all plans for this test of the Founding Titan's power. At the end of Marley's counterattack in Shiganshina District, Eren begins a full-scale rumbling of the entire earth to slaughter all life outside of Paradis Island. Intending to put a stop to Eren's mass genocide, the Yeagerist-opposed members of the Survey Corps join forces with Marley's surviving warriors and head to Paradis's harbor where the flying boat is docked although they find out that the harbor is overrun with Yeagerist forces ready to destroy the flying boat should anyone attempt to commandeer it. Armin Arlert and Connie Springer initially attempt non-hostile coercion to take the flying boat from Samuel and Daz before they can detonate the explosives rigged to the ship but conflict escalates elsewhere in the harbor leading to an all-out battle for the flying boat. The Eldian-Marleyan alliance eventually drives off the Yeagerist forces, escaping by ship with the flying boat in tow.