What must the weather be at an alternate for it to qualify?

For an alternate airport to qualify under aviation regulations, the weather requirements specify that the ceiling must be at least 1,000 feet or 500 feet above the lowest compatible minimum for the approach being flown. This requirement ensures that pilots have adequate visual references on approach to safely operate and land the aircraft, contributing to overall flight safety.

In this context, having a ceiling of at least 1,000 feet or 500 feet above the minimum ensures that if the primary destination airport is not suitable for landing, the alternate airport's weather conditions allow for safe navigation and approach. The alternate can be a critical safety net and must meet these specific minima to provide confidence to pilots during flight planning.

Other choices do not reflect the regulatory requirements for alternate airports. For instance, while a ceiling of 2,000 feet may seem acceptable, it is more stringent than necessary according to regulations. No precipitation expected is not a mandatory requirement for an alternate, and visibility of 5 statute miles, while beneficial for safety, does not directly relate to the regulatory decision regarding ceiling at an alternate airport. Thus, choice B accurately captures the necessary criteria for an alternate airport.