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Range Rings

Planning · April 2026 · 8 min read

Range rings, diversion analysis, and how to use them well

At first glance, a range ring is a trivial concept: draw a circle on a map at a given distance from a point. But like most "obvious" tools, the value is in how you use it. Experienced dispatchers use range rings to answer half a dozen operational questions before the formal flight planning even starts.

The basic idea

A range ring is a circle drawn on a map at a fixed distance — say, 500 nautical miles — from a chosen center point, usually an airport. Anything inside the circle is "within range"; anything outside is "out of range" at that distance.

The distance can be expressed in three useful ways:

In Flight Mapper, range rings support three of those modes: nautical miles, kilometers, and minutes at a configured cruise speed. You can stack as many rings as you want, in different colors and line styles, around different center airports.

Use case 1: Diversion coverage on an oceanic route

The classic use. You have a planned trip from, say, Lisbon (LPPT) to São Paulo (SBGR) — a 4,200-nautical-mile run across the South Atlantic. You want to know: at every point along the route, what's the nearest diversion airport, and how far away is it? See the route with 800-nm diversion rings →

Plot the route. Then drop 800-nm range rings (about 180 minutes at a 270 KT diversion speed for a typical mid-size jet) around the major en-route alternates: Cape Verde (GVAC), Recife (SBRF), Natal (SBNT), Ascension Island (FHAW), Dakar (GOOY). Stack them.

What the map shows you immediately: coverage. Where the rings overlap, you have multiple options. Where they don't, you have a "gap" — a stretch of the route where you're more than 180 minutes from any alternate. For ETOPS-180 commercial operations, that gap is forbidden. For Part 91 business operations it's permitted but considered a risk to be evaluated.

Three minutes of visualization, and the dispatch has a clear go/no-go visual that took the old hand-drawn maps the better part of an hour.

Use case 2: Charter market reach

You operate a fleet of Phenom 300s based in São Paulo. A prospective client asks: "What's your reachable market for a 3-hour nonstop trip?"

Drop a 1,300-nm range ring (roughly 3 hours at the Phenom 300's typical 440-knot cruise) around SBGR. The ring covers all of Brazil, most of South America's major cities, and reaches as far as Caribbean fringes. That's your "3-hour market" — every airport inside the ring is somewhere you can quote nonstop service to in that time budget. See the Phenom 300 reach ring →

Compare to a Citation Latitude (1,000-nm range at 430 KT, about 2.3 hours): smaller ring, smaller market. Versus a Praetor 600 (3,900 nm): a much bigger ring, encompassing most of North America and parts of Europe. Three different aircraft, three different rings, three different commercial propositions, all visible at a glance on the same map.

Use case 3: Aircraft acquisition justification

An owner currently flies a Global 6000 (range about 6,000 nm) and is considering an upgrade to a Global 7500 (range about 7,700 nm). Question: what cities does the upgrade actually unlock from his base?

Drop two rings around the home base: 6,000 nm in one color, 7,700 nm in another. The "shell" between the two — the cities reachable by the 7,500 but not the 6000 — is the answer. If that shell happens to contain cities the owner cares about (London, Geneva, Tokyo, Sydney), the upgrade is justified. If it's mostly open ocean and cities he never visits, it isn't. See the Global 6000 vs 7500 shell from São Paulo →

This is a $40-million-decision conversation in some boardrooms. A 30-second visualization on a map is sometimes all that's needed to settle it.

Use case 4: Ferry leg planning

You're delivering a newly purchased Citation Sovereign from Wichita (KICT) to its new home base in Buenos Aires (SAEZ). Range nonstop: about 3,200 nm. Total trip: about 5,000 nm. Where do you stop?

Drop a 3,200-nm ring around Wichita. The ring covers most of Mexico, much of Central America, and reaches the northern edge of South America near Cartagena and Caracas. Anything inside the ring is a candidate first-leg destination. Anything outside requires two fuel stops.

Looking at the ring's edge, sensible candidates are Panama City (MPTO), Bogotá (SKBO), Caracas (SVMI). Drop a second ring around the candidate of choice — say, Panama City — at 3,200 nm. The new ring reaches all of South America comfortably, including Buenos Aires. Two-leg ferry confirmed: Wichita → Panama → Buenos Aires. See the ferry plan with both rings →

Without the visual, this same analysis takes a dispatch table, a calculator, and twenty minutes of cross-referencing.

Use case 5: Holding/contingency planning

A more operationally subtle use. You have a charter inbound to Aspen (KASE) where the weather forecast is borderline — likely OK at ETA, but with a meaningful chance of a missed approach and divert to Rifle (KRIL), Eagle (KEGE), or Denver (KDEN).

Drop a 100-nm ring around Aspen (about 20 minutes flight time). The ring shows all the candidate alternates in one glance. Now drop a 50-nm ring inside that one. The smaller ring is "very fast divert" — Rifle and Eagle are in it; Denver isn't. Decision: do you carry fuel to reach Denver, or is Rifle/Eagle enough? Visual makes the conversation concrete.

Use case 6: Demonstrating range to a client

Pure sales use, but a powerful one. A prospective charter client asks "can your aircraft reach Cape Town from here?" The answer is "yes" or "no" depending on the specific aircraft, but a yes-no answer isn't as compelling as the visual: drop the aircraft's range ring around the client's location, and let them see Cape Town comfortably inside it. Add a second ring at a different range to compare two aircraft you're offering. The visual sells better than the brochure.

What range rings don't tell you

A few honest limitations:

Wind isn't modeled. Simple range rings assume still air. A westbound transatlantic against the jet stream has dramatically less range than the eastbound trip with the wind, sometimes 15–25 percent. Professional flight planning suites compute "wind-corrected reach" that handles this; Flight Mapper's rings don't.

Reserve fuel isn't subtracted automatically. When you draw a "range" ring you need to decide whether the distance is the aircraft's maximum range (brochure number — never operationally usable) or the practical reach (typically 85–90 percent of max, after subtracting reserves, alternates, and holding fuel). Don't show clients the brochure ring and promise nonstop service — you'll be embarrassed.

Altitude profile is averaged. The same aircraft has different effective ranges at different flight levels, with different weights, and under different temperatures. Range rings show a single average value. Use them for "first cut" thinking; use real flight planning software for the final answer.

Airspace and routing are ignored. The ring shows what's reachable; it doesn't show what's flyable. Restricted airspace, lack of overflight permits, ATC routing penalties — none of that is in the picture. Reality often adds 5–15 percent to the great-circle baseline.

How to use rings in Flight Mapper

In Flight Mapper, the Range Rings section is in the sidebar. Enter a distance and unit, pick a center airport (same search box as routes), choose a color and line style, and click Add Circle. Multiple rings can stack on the same map in different colors. Click any ring's color swatch in the rings list to recolor it; click the trash icon to remove.

For ETOPS analysis specifically: use the "Minutes" unit and set the speed field to your aircraft's one-engine-inoperative cruise speed (typically 270–290 knots for mid-size jets, 290–310 for heavies). 60-minute and 180-minute rings then directly answer "what's reachable from here in N minutes of one-engine-out flight?" — the core ETOPS question.

The takeaway

A range ring is one of those tools whose value scales with the imagination you bring to it. Used mechanically — "draw a circle, see what's inside" — it's mildly useful. Used as a visual reasoning aid for diversion coverage, market reach, ferry planning, fleet decisions, and client conversations, it's a workhorse that experienced dispatchers reach for dozens of times a week.

If you've used Flight Mapper only for plotting routes so far, give the range rings panel an afternoon. Drop a few. Stack them. Look at the same problem from different angles. You'll start seeing operational questions visually instead of arithmetically — and that's a more productive way to think about flight planning.

More reading: ETOPS explained for business aviation · Flight Mapper user guide · Back to blog