What is the worlds shortest runway for FAR 23 commuter type aircraft?
That would be Out Skerries (IATA: OUK) in Shetland with a 1,195 ft / 364 m runway (source).

60°25'30.08" N   0°44'55.93" W

(Source)

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Above plane is a Britten-Norman BN-2 Islander, with a stall speed of 35 knots.


  The Britten-Norman BN-2 Islander is a 1960s British light utility aircraft, regional airliner and cargo aircraft. Still in production, the Islander is one of the best-selling commercial aircraft types produced in Europe.