14 CFR § 135.211

Weather reports or forecasts, or any combination of them, indicate that the weather at the intended point of termination of over-the-top flight—

Allows descent to beneath the ceiling under VFR and is forecast to remain so until at least 1 hour after the estimated time of arrival at that point; or

Allows an IFR approach and landing with flight clear of the clouds until reaching the prescribed initial approach altitude over the final approach facility, unless the approach is made with the use of radar under § 91.175(i) of this chapter; or

It is operated under conditions allowing—

For multiengine aircraft, descent or continuation of the flight under VFR if its critical engine fails; or

For single-engine aircraft, descent under VFR if its engine fails.