From the Airbus A330 FCOM PRO-NOR-SUP-ADVWXR:
SURFACES
CHECK FREE OF FROST, ICE AND SNOW
Check critical surfaces: leading edges, upper wing surfaces, vertical and horizontal stabilizers, all control surfaces, slats and flaps.
Note:Thin hoarfrost is acceptable on the upper surface of the fuselage. Refer to LIM-ICE_RAIN Definition of Thin Hoarfrost.
On the underside of the wing tank areas, a maximum layer of 3 mm (1/8 in.) of frost is acceptable.
(my bold)
Let’s be careful out there. No point trying to save time and money if you won’t be alive to spend it.
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