Where are the tops on your route?
VFR pilots must stay 1,000 ft above the clouds they overfly — so live VFR traffic is a real-world cloud-top sensor. Enter a route; CloudTops reads the traffic, bounds the tops, and shows the NOAA model forecast next to it so you can judge both.
Airports and US VOR/NDBs, separated by spaces, commas, or hyphens —
e.g. KALB-GDM-KPWM or KPVD, PUT, KAUG. RNAV fixes not yet supported.
Route map
Altitude profile along-route distance vs. altitude MSL
What the data says
Where this might be wrong
About the data
Traffic: live ADS-B from adsb.lol (community aggregator), classified LIKELY_VFR / LIKELY_IFR by layered heuristics — squawk 1200, callsign pattern, aircraft type, hemispheric cruise altitude (QNH-corrected), and route databases. Inferred tops: for each ~100 NM segment, if VFR aircraft cruise level ≥1,000 ft above the lowest reported ceiling, tops must lie between that base and the lowest such aircraft minus 1,000 ft. PIREPs corroborate or override the bound — direct observation wins. NOAA layer: GFS model cloud cover by pressure level (via open-meteo.com), converted to altitude with the standard atmosphere — this is the forecast to compare against, not ground truth. Our daily accuracy score is public on the reliability dashboard.