'No speed'

[DFC]

(d) If the minimum safe airspeed for any particular operation is greater than the maximum speed prescribed in this section, the aircraft may be operated at that minimum speed.

I love the common inrepretation of that rule.

Very few people seem to notice that the above rule refers to safety and not in any way to economic or convenient operation.

Therefore, while one could argue that it may indeed be a pain in the ass and is not economic to fly a B747 at 250Kt with flap extended all the way to 10,000 it is 100% safe to do so.

If flying in Class E, F and G there is a hard limit of 250Kt below FL100 / 10,000ft because there is a posibility of encountering unknown VFR traffic and permitting the posibility of "see and avoid".

As was said previously, above FL100 the VMC minima are higher to account for the increrased speed and under ICAO, VFR flight is not normally permitted above FL195.