Gressholmen Seaplane Base

The seaplane base was rendered obsolete and closed for primary commercial traffic following the opening of the new, modern, land-based Oslo Airport, Fornebu, on June 1, 1939. The aviation industry was shifting from seaplanes to more efficient and larger land-based aircraft, which required proper runways. Gressholmen could not accommodate this technological shift, leading to its replacement as Oslo's main international airport.

The site of the former seaplane base is now part of the Gressholmen-Rambergøya Nature Reserve, a protected area established to preserve the island's unique geology, flora, and fauna. It is a popular public recreational area, accessible by ferry from Oslo, offering walking trails, beaches, and a marina. The original airport infrastructure has been repurposed. The main hangar is still standing and is used by the Oslo Fjord Outdoor Recreation Council (Oslofjordens Friluftsråd) for boat storage and maintenance. The former terminal and administration building has been converted into a restaurant and cafe known as 'Gressholmen Kro', preserving a tangible link to its aviation past.

Gressholmen Seaplane Base, opened in 1927, holds significant importance as the first main airport for Oslo and one of the first in Norway. It served as the capital's primary international gateway during the pioneering era of civil aviation. The airport was a crucial hub for the national airline, Det Norske Luftfartselskap (DNL), the forerunner of Scandinavian Airlines (SAS), and the German carrier Deutsche Luft Hansa. Operations primarily involved seaplanes, such as the Junkers G 24 and later the iconic Junkers Ju 52/3m on floats, connecting Oslo with coastal Norwegian towns and international destinations like Copenhagen, Gothenburg, and Berlin. The facility, including its distinctive hangar and terminal building, represented Norway's entry into the international air transport network.

There are no plans or prospects for reopening Gressholmen as an airport. Its status as a protected nature reserve and its established role as a vital public recreational area make any future aviation operations incompatible with its current use and legal protections. The focus for the island is on conservation and public enjoyment, not a return to its original function.