The Port of London Authority (PLA) imposes a 12-knot (14-mph) limit west of Wapping, which means that boats can show their exhilarating 30-knot cruising speed only on the eastern stretches of the river.

ECONOMIST: Thames river transport

Better yet is the jet's 330-knot economy cruise speed, attained at altitudes between 38, 000 and 41, 000 feet.

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In fact, a little computer on the CJ1's center console calculates rotation speed to the knot, based on temperature, altitude and weight aboard.

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