Clean Aircraft Concept
The airline industry, in concert with the FAA, is operating with a clean aircraft concept to minimize the effects of all forms of frozen contamination on aircraft surfaces.
Takeoff is prohibited when frost, ice, snow or slush is adhering to the wings, control surfaces, engine inlets, or other critical surfaces of the aircraft.
•Do not rely on air flow during takeoff roll to remove frozen
precipitation that may be adhering to the aircraft.
•A coating of frost up to 1/8 inch thick on the lower wing surface, below the fuel tank area, is permissible provided it is caused by cold soaked fuel.
•A thin coating of frost is permitted on the fuselage, provided letter and paint lines are visible through the frost.

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Copy and Pasted from my company's operations manual.

Is it safe to say that maybe, just maybe different companies have slightly different operating procedures?

Before you start bashing my company, I assure you our manuals were approved from the FAA. So if you have a problem with the above excerpt that make your complaint with the FAA.

I love the way the Aztec flies