This article about Method 1 and Method 2 gives a brief explanation of Methods 1 and 2 in terms of dispatching flights under 14 CFR 121. Here's an excerpt.

FAR 121.191 requires that we dispatch our aircraft on a routing, weight and expected enroute temperature, that complies with a minimum terrain clearance requirement after an engine failure.

It also requires that we have a plan in place that allows a diversion to an alternate airport enroute, following an engine failure and drift down, with a specific terrain clearance if we do not have the performance to continue to the destination.

My question about flights dispatched under Method 2 concerns route changes. In practice, I'm quite sure that pilots operating aircraft with a Method 2 dispatch release deviate from the planned route on the dispatch all the time. Reasons might include a shortcut request to air traffic control or deviations for weather. Weather deviations seem like the most relevant here because they can sometimes be quite significant.

What additional considerations do pilots have when accepting route changes on flights dispatched under Method 2? Couldn't changing the route render the Method 2 calculations irrelevant?

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    $\begingroup$ I think the title needs to be slightly modified... "Method 2" is not really an industry term, but instead something specific to this page's explanation or possibly Jeppeson's flight planning software and/or JetBlue's GOM. In a more generic sense, pilots might deviate from planned routes where terrain clearance was taken into account in the release. Perhaps: "What additional considerations do pilots have when deviating from the planned routing on flights dispatched with terrain clearance requirements?" (or something like that) $\endgroup$
    – Jimmy
    Commented Feb 28, 2017 at 5:37
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    $\begingroup$ "Method 1" and "Method 2" are common enough that I'd rather make the question more specific than lose that detail. It's a matter of opinion whether or not they are "industry terms." I believe they are from my conversations with pilots from other US 121 pilots. $\endgroup$
    – ryan1618
    Commented Mar 1, 2017 at 0:10

1 Answer 1


As a Former Dispatch Examiner and an Airline Part 121 pilot for most of my career I think what you are looking for is this:

Unless the terrain is such that they must adhere to or close to the desired routing and they are notified of this, most deviations are inconsequential. It also depends on how many engines are on the aircraft. A twin engine aircraft must land at the nearest suitable airport in the point of time after an engine failure. Although it is wise to land with a greater than 2 engine aircraft, that is not the requirement. If an engine fails after takeoff before reaching cruise altitude the PIC should consider terrain clearance in his decision to continue, deviate or return. The PIC is responsible for his decisions and can deviate or not deviate if he feels his decision is as safe as the alternative. After drift down, most jets should clear all terrain with few exceptions but he should always consider obstacle clearance.

Remember everything in preflight must meet regulatory criteria. Once airborne the real world situation can alter and often does alter planning and some regulatory requirements. A lot of planning regulations go away after takeoff. The PIC is the final authority in all decisions after departure even though you both are considered responsible and should agree. If the crew has time to coordinate with Dispatch, then it is the dispatcher's job to warn the crew of all known hazards they may have overlooked while dealing with the in-flight problem even if they were briefed prior to takeoff.


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