diff --git a/src/features/stats/ObserverTab.tsx b/src/features/stats/ObserverTab.tsx
index 639fb06..a90fe0a 100644
--- a/src/features/stats/ObserverTab.tsx
+++ b/src/features/stats/ObserverTab.tsx
@@ -258,7 +258,7 @@ export function ObserverTab({ range, selectedObserverId, onSelectObserver, wsMan
                   option={airtime}
                   isLoading={telemetry.isLoading}
                   isError={telemetry.isError}
-                  isEmpty={missing((p) => p.airtimeTxPct, (p) => p.airtimeRxPct)}
+                  isEmpty={missing((p) => p.airtimeTxSecs, (p) => p.airtimeRxSecs)}
                 />
                 <div className="grid grid-cols-1 gap-3.5 lg:grid-cols-2">
                   <ChartCard title="Battery" height={168} option={battery} isLoading={telemetry.isLoading} isError={telemetry.isError} isEmpty={missing((p) => p.batteryMv)} />
diff --git a/src/features/stats/chartOptions.ts b/src/features/stats/chartOptions.ts
index ca5d790..b4154fd 100644
--- a/src/features/stats/chartOptions.ts
+++ b/src/features/stats/chartOptions.ts
@@ -324,8 +324,8 @@ export function airtimeOption(points: TelemetryPoint[], c: ChartColors, bucketMs
     xAxis: timeAxis(c),
     yAxis: percentAxis(c),
     series: [
-      { name: "RX", type: "line", stack: "air", smooth: true, symbol: "none", connectNulls: true, data: airtimePctSeries(points, "airtimeRxPct", bucketMs), lineStyle: { width: 1, color: c.green }, areaStyle: { color: withAlpha(c.green, 0.35) }, itemStyle: { color: c.green } },
-      { name: "TX", type: "line", stack: "air", smooth: true, symbol: "none", connectNulls: true, data: airtimePctSeries(points, "airtimeTxPct", bucketMs), lineStyle: { width: 1, color: c.primary }, areaStyle: { color: withAlpha(c.primary, 0.35) }, itemStyle: { color: c.primary } },
+      { name: "RX", type: "line", stack: "air", smooth: true, symbol: "none", connectNulls: true, data: airtimePctSeries(points, "airtimeRxSecs", bucketMs), lineStyle: { width: 1, color: c.green }, areaStyle: { color: withAlpha(c.green, 0.35) }, itemStyle: { color: c.green } },
+      { name: "TX", type: "line", stack: "air", smooth: true, symbol: "none", connectNulls: true, data: airtimePctSeries(points, "airtimeTxSecs", bucketMs), lineStyle: { width: 1, color: c.primary }, areaStyle: { color: withAlpha(c.primary, 0.35) }, itemStyle: { color: c.primary } },
     ],
   };
 }
diff --git a/src/features/stats/transforms.ts b/src/features/stats/transforms.ts
index 4f76bc2..cf8fd4d 100644
--- a/src/features/stats/transforms.ts
+++ b/src/features/stats/transforms.ts
@@ -37,8 +37,8 @@ export function hasTelemetry(points: TelemetryPoint[]): boolean {
   return points.some(
     (p) =>
       live(p.batteryMv) ||
-      live(p.airtimeTxPct) ||
-      live(p.airtimeRxPct) ||
+      live(p.airtimeTxSecs) ||
+      live(p.airtimeRxSecs) ||
       live(p.noiseFloorDb) ||
       live(p.uptimeSeconds) ||
       live(p.queueLength) ||
@@ -59,9 +59,9 @@ function pct(seconds: number, windowSeconds: number): number {
   return Math.round(((seconds * 100) / windowSeconds) * 1000) / 1000;
 }
 
-type AirtimeKey = "airtimeRxPct" | "airtimeTxPct";
+type AirtimeKey = "airtimeRxSecs" | "airtimeTxSecs";
 
-// The values are on-air seconds despite the field name: cumulative on raw 1h points, per-bucket on
+// The values are on-air seconds: cumulative on raw 1h points, per-bucket on
 // bucketed ones. Chart the increase as a percent of the elapsed time, clamped at 0 on counter resets.
 export function airtimePctSeries(points: TelemetryPoint[], key: AirtimeKey, bucketMs: number | null): [number, number | null][] {
   if (bucketMs != null) {
@@ -88,7 +88,7 @@ export function latestAirtimePct(points: TelemetryPoint[], bucketMs: number | nu
     const s = airtimePctSeries(points, key, bucketMs);
     return s.length ? s[s.length - 1]![1] : null;
   };
-  return { rx: last("airtimeRxPct"), tx: last("airtimeTxPct") };
+  return { rx: last("airtimeRxSecs"), tx: last("airtimeTxSecs") };
 }
 
 // The server skips empty buckets; fill them so a quiet stretch draws as zero instead of a skipped line.
diff --git a/src/features/stats/types.ts b/src/features/stats/types.ts
index 3d4138e..628d787 100644
--- a/src/features/stats/types.ts
+++ b/src/features/stats/types.ts
@@ -99,8 +99,8 @@ export interface ScopeStats {
 export interface TelemetryPoint {
   t: number; // epoch ms
   batteryMv: number | null;
-  airtimeTxPct: number | null; // on-air seconds despite the name: cumulative on 1h points, per-bucket otherwise
-  airtimeRxPct: number | null;
+  airtimeTxSecs: number | null; // cumulative since boot on 1h points, per-bucket delta otherwise
+  airtimeRxSecs: number | null;
   noiseFloorDb: number | null;
   uptimeSeconds: number | null;
   queueLength: number | null;