About SimNavLog
Who makes it
One developer, in their spare time, because they wanted it to exist. A flight simulation enthusiast — not a pilot, not an instructor, and not anyone with an aviation qualification of any kind. What is implemented here was learned from textbooks and public material, and it is implemented well enough to be interesting in a simulator and nowhere near well enough to be trusted anywhere else.
It is free to use, and it will stay free to use for planning a flight. There is no advertising, no analytics and no tracking cookies — the only cookies it sets are the ones that keep you signed in and keep the forms safe. Nothing you type here is sold, shared or handed to anyone for their own purposes, and you can delete all of it from your account settings whenever you like; the privacy policy says the same at length.
If you want the longer version of what an account adds, that is on the Free & Supporter page.
The sources that make it possible
Almost every number in a nav log comes from somewhere else. The airspace, the charts, the weather, the terrain, the airfields, the magnetic variation — all of it is collected, maintained and given away by people and organisations with no connection to this project. SimNavLog is mostly a way of arranging their work on a sheet of paper.
openAIP, in particular
The airspace layer exists because of openAIP. Airspace volumes, their vertical limits and their frequencies are published for the whole world by a volunteer community, and there is no free alternative that covers the globe. Without openAIP, SimNavLog would have no airspace to show you anywhere.
Asked in September 2026 how a project like this could support them, they said there is currently no way to pay — and asked instead that we spread the word and contribute data back. This page is the first half of that. The second half is the section below, and it is open to you as much as to us.
Aeronautical and weather data
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openAIP
CC BY-NC 4.0
Airspace volumes, their vertical limits and ATC frequencies, and VFR reporting points — worldwide. There is no free global alternative to openAIP: without it there is no airspace layer, anywhere. It also draws the worldwide aviation overlay, which is what a route outside Europe and the US has instead of a chart.
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Aviation Weather Center
public domain
The METARs behind the weather cards: reported wind, visibility, cloud, temperature and pressure at the airfields along the route.
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MET Norway
CC BY 4.0
A second source for the same METARs, genuinely independent of NOAA. It carried the complete half-hourly series through a four-hour gap in the primary feed.
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NOAA tgftp
a US Government work not subject to copyright
The last resort for a METAR: the raw observation files the US National Weather Service publishes, on a different pipeline from the one behind the Aviation Weather Center's API.
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NOAA / NCEP GFS
a US Government work not subject to copyright
Forecast wind and temperature at cruising altitude — the numbers the wind correction angle, true heading and ground speed are computed from. The Global Forecast System, run four times a day.
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U.S. Geological Survey
public domain
Ground elevation along the route, behind the terrain profile and the minimum safe altitude it suggests for each leg.
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Natural Earth
public domain
Where the sea is. The elevation data carries ocean bathymetry, so the terrain profile needs to know which negative readings are the sea floor and which are land genuinely below sea level.
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OurAirports
public domain
Airports, runways, navaids and radio frequencies — the lookup behind every waypoint you type an identifier for.
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GeoNames
CC BY 4.0
The named places, peaks, lakes and islands SimNavLog offers as checkpoint names — the towns and hills a VFR pilot navigates by, rather than the airfields they land on.
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NOAA NCEI / BGS
a US Government work not subject to copyright
The magnetic model SimNavLog computes variation from, locally, for every point on the route — the step from true course to magnetic.
Maps and charts
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OpenFreeMap
ODbL
The default base map under the route. It labels places in the Latin alphabet *and* the local script — Tokyo over 東京都 — so a route can be checked against the ground anywhere, not only where the place names happen to be readable.
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OpenStreetMap
ODbL
The raster base map — roads, towns, coastlines, lakes — drawn by a global volunteer community. What the map falls back to where the vector one cannot be rendered.
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OpenTopoMap
CC-BY-SA
The shaded-relief base map, for seeing the shape of the ground a route crosses before the terrain profile confirms it.
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Open Flightmaps
OFMA General Users' License
The European VFR chart layer — a real aeronautical chart to draw the route on, produced by volunteers and given away.
Covers much of western, central and northern Europe — AT, BE, BG, CH, CZ, DE, DK, FI, FR, GR, HR, HU, IT, LU, MD, MT, NL, PL, RO, SE, SI, SK.
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FAA
public domain
The US VFR sectional chart layer, published by the FAA.
Covers the United States — US.
Software running in your browser
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Leaflet
BSD-2-Clause
The map itself. Every layer, marker, route line and drag in the browser is Leaflet doing the work.
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MapLibre GL JS
BSD-3-Clause
Draws the default base map. Its tiles are vector rather than pictures, which is what lets the labels be rendered in two scripts at once — and what makes a WebGL renderer necessary. It runs inside the Leaflet map, as one layer.
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maplibre-gl-leaflet
ISC
Puts the MapLibre renderer inside the Leaflet map as an ordinary base layer, so every marker, route line, drag handler and pane above it went on working untouched when the base map became vector.
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MDEx
MIT
Turns what a pilot writes — a tour's briefing, a note on a stop or a flight — from Markdown into the page you read, with raw HTML escaped and dangerous links left empty.
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comrak
BSD-2-Clause
The Markdown parser inside MDEx: CommonMark and GitHub-flavoured Markdown, in Rust, running on the server.
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Open-Meteo
AGPL-3.0 (server), CC BY 4.0 (data)
The weather server SimNavLog runs alongside itself: it ingests NOAA's GFS forecasts and answers the wind and temperature queries behind every leg. Run unmodified — the link is its complete source.
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HeroIcons
MIT
The interface icons throughout the application.
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Astigmatic
Apache-2.0
The handwriting face the nav log is filled in with, and the reason a printed sheet looks like a sheet somebody wrote on.
Help improve the data
Several of these sources are edited by the people who use them, which means a report is a fix rather than a ticket: correct it once and everyone reading that data gets the correction, whatever application they use it in. If SimNavLog shows you something wrong, this is where it actually gets better.
OpenFreeMap
The place names and coastlines here are OpenStreetMap's, and anyone may correct them. A fix reaches this map on the next planet build rather than only SimNavLog.
OpenStreetMap
A wrong road, town or coastline on the base map is OpenStreetMap's to fix, and anyone may fix it. Dropping a note on the map takes a moment and needs no account.
Open Flightmaps
Report a chart error by email. The open flightmaps licence asks every user to report errors as they find them, and asks applications built on the data to offer their users a way to do the same — this is ours.
openAIP
openAIP is crowd-sourced. With a free account you can find the airspace or airfield and file a change request against the record itself, and the fix reaches everyone using openAIP rather than only SimNavLog.
OurAirports
Community-edited. A free account lets you correct an airport record directly, and every airport page carries a problem-report form if you would rather just say what looks wrong.
GeoNames
Community-edited. A free account lets you correct a name, a position or a population directly, and every place has an edit page.
Please check the official publication for the country concerned before reporting something as wrong. These are volunteer projects, and a mistaken report costs somebody an evening.
Support the sources
A few of these projects serve SimNavLog at their own expense and publish a way to be paid back for it. None of this comes to SimNavLog — these are their own donation pages, the money goes to them, and we neither receive nor handle any of it.
OpenFreeMap
OpenFreeMap is run by one person, Zsolt Ero, and given away with no key and no request limit. The project asks for recurring donations because the planet-sized servers under it are a recurring cost.
OpenStreetMap
The base map under every route is OpenStreetMap's, served from the Foundation's own tile servers. Donations pay for the hardware and the bandwidth.
Open Flightmaps
Every chart tile SimNavLog draws is served from open flightmaps' own API, at their expense — they told us so, and opened it to us anyway. Donating is the thing they asked for.
The others are not listed because they take no donations, not because they cost nothing. Several said so when asked; for them, the sections above — the credit and the corrections — are what they asked for instead.