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The Dassault Mercure was a French regional jet that first flew in 1971 and received its type certificate in February 1974; it resembled an enlarged, shorter-range 737-200, and was designed to serve higher-capacity short-haul routes. The Mercure was an abysmal failure, with only eleven aircraft ever sold, all to French domestic carrier Air Inter. Wikipedia states, citing Dassault’s own website, that the killer was its short range, only 2,080 km (1,125 nmi) with a typical payload, and reducing to 1,700 km (920 nmi) at maximum capacity.

Except... that doesn’t actually explain the Mercure’s failure to sell!

Sure, it didn’t have the range for long transcontinental or transoceanic crossings, but you don’t need that much range to be successful as an airliner, as evidenced by the profits made by regional-jet manufacturers. The Mercure’s Wikipedia article - citing Dassault - admits as much, even as it makes the claim that the aircraft was doomed by its short range:

This lack of interest was due to several factors, including the devaluation of the dollar and the oil crisis of the 1970s, but mainly because of the Mercure's operating range – suitable for domestic European operations but unable to sustain longer routes; at maximum payload, the aircraft's range was only 1,700 km. [emphasis added]

1,700 km is plenty of range for European routes, and there are numerous other markets for high-capacity, short-range aircraft. Japan, land of the 747 regional jet, comes immediately to mind, along with the other dense areas of East, Southeast, and South Asia and the Middle East. Even infamously-spread-out North America should have been fertile ground, what with the multitudes of short routes (and even not-so-short ones; the Mercure would have had enough range to comfortably fly between New York and Chicago in a typical passenger configuration, although not in all-up sardine mode) in the northeastern and midwestern United States, eastern Canada, parts of the South, the West Coast, and the Caribbean. As a point of comparison, the earlier Sud Caravelle - the fourth jetliner to enter revenue service,¹ and the first-ever regional jet - had an even shorter range (1,700 km was its maximum range), and it was riotously successful, to the tune of 282 aircraft (some of the very last of these, ironically, going to Air Inter at the very same time they were contemplating the Mercure), despite also having a smaller passenger capacity.

What am I missing? Why wasn’t the Dassault Mercure successful in the short-haul market?

¹: Preceded by the Comet, the Tu-104, and the 707, in that order.

Mainly because the short haul market needed to wait for the deregulation of the late 70s into the early 80s that resulted in the creation, by the early 90s, of the hub and spoke concept with small regional jets feeding hubs where the mainliners were.

The CRJ200 was the main pioneer of this market, as an up to date rendition of a smaller regional feeder jet. At the time it was expected to sell maybe a couple hundred units, even within Canadair.