Existem regulamentações sobre a distância entre aeroportos de destino e alternativos?

Em um plano de voo IFR, 14 CFR 135.233 requer

§ 135.223 IFR: Alternate airport requirements.

(a) Except as provided in paragraph (b) of this section, no person may operate an aircraft in IFR conditions unless it carries enough fuel (considering weather reports or forecasts or any combination of them) to—

    (1) Complete the flight to the first airport of intended landing;

    (2) Fly from that airport to the alternate airport; and

    (3) Fly after that for 45 minutes at normal cruising speed or, for helicopters, fly after that for 30 minutes at normal cruising speed.

Restrição do outro lado, 14 CFR 91.169 requer

(c) IFR alternate airport weather minima. Unless otherwise authorized by the Administrator, no person may include an alternate airport in an IFR flight plan unless appropriate weather reports or weather forecasts, or a combination of them, indicate that, at the estimated time of arrival at the alternate airport, the ceiling and visibility at that airport will be at or above the following weather minima:

    (1) If an instrument approach procedure has been published inpart 97 of this chapter, or a special instrument approach procedure has been issued by the Administrator to the operator, for that airport, the following minima:

        (i) For aircraft other than helicopters: The alternate airport minima specified in that procedure, or if none are specified the following standard approach minima:

            (A) For a precision approach procedure. Ceiling 600 feet and visibility 2 statute miles.

            (B) For a nonprecision approach procedure. Ceiling 800 feet and visibility 2 statute miles.

        (ii) For helicopters: Ceiling 200 feet above the minimum for the approach to be flown, and visibility at least 1 statute mile but never less than the minimum visibility for the approach to be flown, and

A distância máxima para um aeroporto alternativo é limitada pela faixa de combustível da sua aeronave, mas a praticidade (não perder o objetivo da viagem) tenderá a ser mais restritiva do que a matemática. A distância mínima depende do tempo.