A Reddit thread posing a historical fiction research question—what aircraft a wealthy private individual might have used to cross the Atlantic in 1939, routing from Athens to London to a clandestine Greenland airstrip before arriving in New York—highlights just how radically different transatlantic air travel was on the eve of World War II compared to today. In 1939, there was no such thing as a "private plane" capable of ocean crossings in the modern sense. The only aircraft with the range, reliability, and infrastructure to attempt such a journey were large flying boats operated by commercial carriers, chiefly Pan American Airways. Pan Am's Boeing 314 Clipper began the first scheduled transatlantic passenger service in June 1939, flying the northern route via Newfoundland, or the southern route via the Azores and Lisbon, with fuel stops built in because no aircraft of the era could cross nonstop with a meaningful payload. A private citizen wanting to make that trip would almost certainly have had to charter passage on, or lease outright, a Clipper-type flying boat or a similarly configured long-range aircraft like the Sikorsky S-42, since dedicated business aircraft as understood today simply did not exist.
The staffing requirement is where the historical fiction detail gets particularly interesting for pilots familiar with modern crew concepts. These aircraft were not flown by a single captain and first officer the way a contemporary Gulfstream or Global Express would be. A Boeing 314 or S-42 required a full flight deck crew of four to seven, typically including a captain, first officer, second officer, flight engineer, navigator, and radio operator, reflecting the navigational and mechanical complexity of long-range overwater flight before radar, GPS, or reliable radio direction finding existed. Dead reckoning, celestial navigation, and radio bearings were the only tools available, and weather forecasting was rudimentary at best. This means any private group attempting the Athens-London-Greenland-New York routing in the novel would need not just "more than one pilot" but essentially a professional maritime-style crew, comparable in scale and specialization to crewing an oceangoing yacht rather than hopping in a two-pilot jet.
The Greenland stop is worth flagging as a likely anachronism worth researching further. Greenland had no developed airfield infrastructure in 1939; the Bluie West and Bluie East airbases that later became critical to the transatlantic ferry route for military aircraft were constructed starting in 1941, specifically to support Lend-Lease and combat aircraft deliveries to Britain. A "private, secretive airfield" in Greenland in 1939 would be fictional invention rather than historical fact, though that may be entirely acceptable for a novel depending on how much creative license the author wants. If historical accuracy matters, an alternative routing through the Azores, Newfoundland, or Iceland would better reflect actual 1939-era infrastructure and Pan Am's established stopping points.
For working pilots reading this exchange, the thread is a useful reminder of how compressed aviation's technological timeline really is. The gap between the flying-boat era's multi-stop, multi-crew ocean crossings and today's single-pilot-capable business jets flying nonstop from New York to London in under seven hours spans less than a century, and much of that progress—pressurization, turbine engines, inertial and satellite navigation, ETOPS certification—was driven directly by the operational lessons learned flying exactly the kind of aircraft this novelist is researching. It also underscores why business aviation history buffs and type-club researchers remain a valuable resource for authors: getting crew composition, range limitations, and period-accurate infrastructure right is often the difference between a technically credible period piece and one that breaks immersion for readers who know the aircraft.