There is one niche that may be of interest for commercial application, a very large cargo lifter biplane. Once wingspan reaches a certain length, even modern materials and designs reach limits due sheer size.

While 250 knots is considered extremely fast for a train, it is a long forgotten mode of travel for aircraft, with potentially enormous fuel savings. Coast to coast in the USA would be around 10 hours of flight time.

Combined with turboprops for regional next day regional cargo runs or mail, this could be a real money maker, with nostalgic appeal, and in safety in strength without the need for folding wings.

There is one niche that may be of interest for commercial application, a very large cargo lifter biplane. Once wingspan reaches a certain length, even modern materials and designs reach limits due sheer size.

While 250 knots is considered extremely fast for a train, it is a long forgotten mode of travel for aircraft, with potentially enormous fuel savings. Coast to coast in the USA would be 10 hours of flight time. New York to Florida around 5 hours.

Combined with turboprops for regional next day cargo runs or mail, this could be a real money maker, with nostalgic appeal, and with safety in strength without the need for folding wings. Passengers could also ride low budget.