Ar det några regler om avståndet mellan destination och alternativa flygplatser?

På en IFR-flygplan kräver 14 CFR 135.233

§ 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.

Begränsning från andra sidan, kräver 14 CFR 91.169

(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

Det maximala avståndet för en alternativ flygplats är begränsad av flygplanets bränslesortiment, men praktiska (förlorar inte resans syfte) tenderar att vara mer begränsande än matte. Minsta avstånd beror på vädret.

Mot bakgrund av det här perspektivet, med tanke på att målet är säkerhet, att "minst X men inte mer än Y-enheter av avstånd " skulle vara olämpliga av liknande skäl till varför vi tenderar att < a href="http://aviation.stackexchange.com/q/8834/2143"> Tänk på bränsle när det gäller tid snarare än längd .