The NC-4 aircraft arrives in Lisbon after completing the first transatlantic flight.

The NC-4 is a Curtiss NC flying boat that was the first aircraft to fly across the Atlantic Ocean, albeit not non-stop. The NC designation was derived from the collaborative efforts of the Navy (N) and Curtiss (C). The NC series flying boats were designed to meet wartime needs, and after the end of World War I they were sent overseas to validate the design concept.

Lisbon is the capital and largest city of Portugal, with an estimated population of 575,739, as of 2024, within its administrative limits and 3,028,000 within the metropolis, as of 2025. Lisbon is mainland Europe's westernmost capital city, and the only one along the Atlantic coast, the others being on islands. The city lies in the western portion of the Iberian Peninsula, on the northern shore of the River Tagus. The western portion of its metro area, the Portuguese Riviera, hosts the westernmost point of Continental Europe, culminating at Cabo da Roca.

A transatlantic flight is the flight of an aircraft across the Atlantic Ocean from Europe, Africa, South Asia, or the Middle East to North America, South America, or vice versa. Such flights have been made by fixed-wing aircraft, airships, balloons and other aircraft.