In July 1930, journalists, MPs, and industrialists boarded a strange aluminum carriage suspended from an overhead gantry above the LNER railway line at Milngavie, just outside Glasgow. Two four-bladed propellers — one at each end — spun up. The carriage accelerated smoothly along a 130-metre test track built parallel to existing rails. This was the Bennie Railplane, and its inventor, George Bennie, was quietly convinced he had made the steam locomotive obsolete.

Bennie, a Glasgow engineer, patented the concept in 1921. The idea was elegant: separate high-speed passenger traffic from slow freight by hanging a streamlined, propeller-driven car from an overhead rail while a second lower rail provided lateral stability. Freight kept the ground-level tracks. Passengers flew above at speeds no steam locomotive could touch. The published design target was 120 mph — twice the express speeds of the era — and independent engineers who examined the aerodynamics agreed the number was plausible.

The Milngavie prototype cost Bennie roughly £150,000 of his own money (about £12 million today). It worked. The carriage seated a dozen passengers, had wicker chairs, curtains, a lavatory, and enough acceleration to be genuinely uncomfortable. Reviews were rapturous. The Times, Flight magazine, and Pathé newsreels all covered it. Bennie negotiated seriously with the governments of Iraq (for a Baghdad–Basra route), Palestine, and later Southern Rhodesia.

Then the Depression hit. Every proposed contract evaporated. LNER, which had tolerated the test rig on its property, wanted its land back. Bennie personally bankrupted himself keeping the prototype standing. He died in 1957 having never built a revenue line. The Milngavie gantry was scrapped in 1956 for £375.

Why revisit it in 2026? Three things have changed:

• Electric ducted fans have replaced open propellers. Bennie's original hazard — spinning wooden blades near passengers — is gone. Modern EDFs used in eVTOL aircraft (Joby, Lilium) run at 90%+ efficiency and are quiet enough for urban corridors. Bolt two to a suspended pod and you have his design without the safety objection.
• Overhead structures dodge the land-acquisition death spiral. High-speed rail routinely dies because you cannot buy a straight line through populated country. A suspended railplane runs above existing rail corridors, motorways, or canals — right-of-way already owned, no new expropriation. This is exactly what Chiba's suspended monorail (still running since 1988) proves at low speed.
• Aluminum-lithium and CFRP make Bennie's aluminum carriage 60% lighter. The original weighed 8 tonnes. A modern equivalent would be under 3, cutting energy per passenger-km below any conventional rail.

The economics were never the problem. A 1932 study by consulting engineers Sir Alexander Gibb estimated the Baghdad–Basra route at £3,000 per mile of gantry versus £15,000 per mile for conventional double-track railway — and the railplane needed no tunnels, no level crossings, no signaling infrastructure. What killed it was timing: 1930 was the worst possible year in the 20th century to ask governments for infrastructure capital.

The Shanghai Maglev cost roughly $50 million per kilometre. A modern Bennie-style EDF railplane on existing corridors would be a fraction of that, at speeds competitive with regional aviation. Bennie was not wrong. He was early, and then he was broke.