Opening in 1974 the DFW Airtrans APM was probably the largest and most extensive airport transport system to have been built anywhere globally.
Whereas most airport people-movers usually just shuttle to and fro between two stations (and possibly calling at an intermediate station or two) this one was different as it was 15 miles (24km) in length and featured over 30 stations.
So it was more like a transit system for a small town(!) providing a variety of services serving different stations and featuring one, two and three car formations.
The fleet consisted of 68 cabin-sized vehicles which seated 16 passengers and offered standing room for a further 24 passengers. The system had an overall capacity rated at 9,000 people/hr. The top speed was just 17mph (27km/h).
Although there were some initial teething problems it eventually became very reliable. During its 31 years of operation there were many technical upgrades, some of which took advantage of advancing technology, eg: circuit boards were replaced with microchips and the original eight-track cartridge system which was used for the passenger announcements was later updated to a compact cassette system and still later to a digital voice synthesizer.
Although very successful it suffered from a few shortcomings and these, combined with changes in how the airport operated (the rise of the 'spoke and hub' system meant that an increasing number of passengers changed flights here) caused its eventual demise.
Its closure was partly because services operated as a one-way loop which coupled with the somewhat sedate top speed meant that some journeys took much longer in one direction than the other direction (possibly as much as 30+ minutes), resulting in transfer times being too long for passengers on multi-stage journeys where they also needed to change terminals when changing flights here.
In 2003 the airport staff and 'non-secure' passenger services were replaced by contracted-out motor bus services - airports were never known for their environmental credentials so its very unlikely that anyone even considered the extra air pollution from the motor bus exhaust fumes.
The APM closed in 2005, replaced by an airside (ie: 'secure') people-mover dedicated to speeding passengers between terminals known as the 'Skylink' and which (like the former APM) is electrically operated.
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Additional Information:
Despite not serving the car parks, hotels, etc., Skylink is now the largest airport people-mover system anywhere globally. Its 64-vehicle fleet serves 10 stations on 5 miles (8km) of two-way elevated guideways. Services run every two minutes and travel at speeds up to 37mph (60km/h) with an average passenger ride time of just 5 to 8 minutes. (Skylink is not seen in this video).