sensors Mode-S transponder
A4FFB7
ICAO 24-bit transponder address · allocated to United States
Currently assigned to N421DX · AIRBUS A-330-900 · operated by DELTA AIR LINES INC
- Hex
- A4FFB7
- Octal
- 51177667
- Decimal
- 10,813,367
- Country
- US
- Tail
- N421DX
- Type
- A339
- Flights observed
- 310
- Distinct callsigns
- 20
- Country
- US
- Last broadcast
- Jul 26, 19:55 UTC
Current position
Country allocation
The ICAO 24-bit address A4FFB7 falls within the block assigned to United States (US) by ICAO Annex 10, Volume III. Every aircraft registered in United States receives a permanent address from this block at the time of registration; the address stays with the airframe even if the aircraft is re-registered to a different operator within the country.
Callsign history 20 distinct
| Callsign | Airline | Flights | Last seen |
|---|---|---|---|
| DAL17 | Delta Air Lines | 12 | 2026-06-23 |
| DAL16 | - | 11 | 2026-06-22 |
| DAL133 | - | 11 | 2026-06-27 |
| DAL213 | - | 9 | 2026-07-19 |
| DAL157 | - | 9 | 2026-07-11 |
| DAL132 | - | 9 | 2026-06-27 |
| DAL66 | Delta Air Lines | 8 | 2026-06-07 |
| DAL241 | - | 8 | 2026-07-05 |
| DAL222 | - | 8 | 2026-07-04 |
| DAL215 | - | 8 | 2026-07-04 |
| DAL143 | - | 8 | 2026-06-28 |
| DAL224 | - | 7 | 2026-07-06 |
| DAL214 | Delta Air Lines | 7 | 2026-07-03 |
| DAL67 | Delta Air Lines | 6 | 2026-06-08 |
| DAL63 | Delta Air Lines | 6 | 2026-07-26 |
| DAL59 | - | 6 | 2026-06-19 |
| DAL58 | - | 6 | 2026-06-15 |
| DAL243 | Delta Air Lines | 6 | 2026-07-24 |
| DAL240 | Delta Air Lines | 6 | 2026-07-24 |
| DAL56 | - | 5 | 2026-07-07 |
Recent flights last 50
| Date | Flight | Route | Takeoff | Landing | Duration |
|---|---|---|---|---|---|
| 2026-07-26 | DAL63 | FCO → ATL | Jul 26, 12:50 UTC | Jul 26, 14:05 UTC | 1h 15m |
| 2026-07-26 | DAL63 | FCO → ATL | Jul 26, 12:48 UTC | Jul 26, 19:45 UTC | 6h 57m |
| 2026-07-26 | DAL108 | ATL → MAD | Jul 26, 02:10 UTC | Jul 26, 10:20 UTC | 8h 11m |
| 2026-07-25 | DAL223 | ATH → ATL | Jul 25, 07:10 UTC | Jul 25, 11:20 UTC | 4h 10m |
| 2026-07-25 | DAL223 | ATH → ATL | Jul 25, 07:08 UTC | Jul 25, 18:16 UTC | 11h 8m |
| 2026-07-24 | DAL240 | BOS → ATH | Jul 24, 19:50 UTC | Jul 25, 04:09 UTC | 8h 19m |
| 2026-07-24 | DAL240 | BOS → ATH | Jul 24, 19:50 UTC | Jul 24, 21:00 UTC | 1h 10m |
| 2026-07-24 | DAL243 | TLV → BOS | Jul 24, 09:40 UTC | Jul 24, 16:40 UTC | 7h 0m |
| 2026-07-23 | DAL142 | SEA → AMS | Jul 23, 21:25 UTC | Jul 24, 06:10 UTC | 8h 45m |
| 2026-07-22 | DAL21 | LHR → SEA | Jul 22, 17:30 UTC | Jul 22, 18:45 UTC | 1h 15m |
| 2026-07-22 | DAL21 | LHR → SEA | Jul 22, 17:28 UTC | Jul 23, 03:24 UTC | 9h 56m |
| 2026-07-22 | DAL20 | - | Jul 22, 05:00 UTC | Jul 22, 05:25 UTC | 25m |
| 2026-07-22 | DAL20 | SEA → LHR | Jul 22, 04:57 UTC | Jul 22, 13:45 UTC | 8h 48m |
| 2026-07-21 | DAL81 | - | Jul 21, 14:30 UTC | Jul 21, 15:45 UTC | 1h 15m |
| 2026-07-21 | DAL81 | CDG → SEA | Jul 21, 14:25 UTC | Jul 22, 00:24 UTC | 9h 59m |
| 2026-07-21 | DAL80 | SEA → CDG | Jul 21, 02:00 UTC | Jul 21, 11:20 UTC | 9h 20m |
| 2026-07-21 | DAL80 | SEA → CDG | Jul 21, 02:05 UTC | Jul 21, 05:25 UTC | 3h 20m |
| 2026-07-20 | DAL145 | AMS → SEA | Jul 20, 13:40 UTC | Jul 20, 23:30 UTC | 9h 50m |
| 2026-07-20 | DAL164 | MSP → AMS | Jul 20, 03:13 UTC | Jul 20, 10:55 UTC | 7h 42m |
| 2026-07-20 | DAL164 | MSP → AMS | Jul 20, 03:15 UTC | Jul 20, 04:05 UTC | 50m |
| 2026-07-19 | DAL165 | AMS → MSP | Jul 19, 14:25 UTC | Jul 19, 22:40 UTC | 8h 15m |
| 2026-07-19 | DAL165 | AMS → MSP | Jul 19, 14:25 UTC | Jul 19, 22:35 UTC | 8h 10m |
| 2026-07-19 | DAL48 | JFK → AMS | Jul 19, 05:25 UTC | Jul 19, 12:05 UTC | 6h 40m |
| 2026-07-19 | DAL213 | - | Jul 19, 01:20 UTC | Jul 19, 01:40 UTC | 20m |
| 2026-07-18 | DAL213 | ATH → JFK | Jul 18, 14:57 UTC | Jul 19, 01:02 UTC | 10h 5m |
| 2026-07-18 | DAL213 | ATH → JFK | Jul 18, 14:57 UTC | Jul 19, 01:42 UTC | 10h 45m |
| 2026-07-18 | DAL213 | - | Jul 18, 15:00 UTC | Jul 18, 19:15 UTC | 4h 15m |
| 2026-07-18 | DAL212 | JFK → ATH | Jul 18, 03:30 UTC | Jul 18, 12:30 UTC | 9h 0m |
| 2026-07-17 | DAL203 | ATH → JFK | Jul 17, 07:25 UTC | Jul 17, 17:40 UTC | 10h 15m |
| 2026-07-16 | DAL202 | - | Jul 16, 19:35 UTC | Jul 16, 21:05 UTC | 1h 30m |
| 2026-07-16 | DAL202 | JFK → ATH | Jul 16, 19:32 UTC | Jul 17, 04:18 UTC | 8h 46m |
| 2026-07-15 | DAL939 | LAX → JFK | Jul 15, 18:40 UTC | Jul 16, 00:00 UTC | 5h 20m |
| 2026-07-15 | DAL939 | LAX → JFK | Jul 15, 18:38 UTC | Jul 15, 23:49 UTC | 5h 11m |
| 2026-07-15 | DAL742 | JFK → LAX | Jul 15, 11:40 UTC | Jul 15, 16:25 UTC | 4h 45m |
| 2026-07-14 | DAL213 | ATH → JFK | Jul 14, 12:45 UTC | Jul 14, 22:52 UTC | 10h 7m |
| 2026-07-14 | DAL213 | ATH → JFK | Jul 14, 12:45 UTC | Jul 14, 22:46 UTC | 10h 1m |
| 2026-07-14 | DAL213 | ATH → JFK | Jul 14, 12:45 UTC | Jul 14, 22:55 UTC | 10h 9m |
| 2026-07-14 | DAL212 | JFK → ATH | Jul 14, 01:09 UTC | Jul 14, 10:05 UTC | 8h 56m |
| 2026-07-14 | DAL212 | - | Jul 14, 01:10 UTC | Jul 14, 07:45 UTC | 6h 35m |
| 2026-07-13 | DAL203 | ATH → JFK | Jul 13, 07:25 UTC | Jul 13, 17:30 UTC | 10h 5m |
| 2026-07-12 | DAL202 | - | Jul 12, 19:30 UTC | Jul 13, 04:25 UTC | 8h 55m |
| 2026-07-12 | DAL202 | JFK → ATH | Jul 12, 19:26 UTC | Jul 13, 04:22 UTC | 8h 56m |
| 2026-07-12 | DAL273 | LIS → JFK | Jul 12, 09:40 UTC | Jul 12, 16:30 UTC | 6h 50m |
| 2026-07-12 | DAL272 | JFK → LIS | Jul 12, 01:20 UTC | Jul 12, 07:25 UTC | 6h 5m |
| 2026-07-11 | DAL157 | - | Jul 11, 11:45 UTC | Jul 11, 19:40 UTC | 7h 55m |
| 2026-07-11 | DAL157 | - | Jul 11, 03:45 UTC | Jul 11, 19:40 UTC | 15h 55m |
| 2026-07-10 | DAL157 | - | Jul 10, 21:50 UTC | Jul 11, 19:40 UTC | 21h 50m |
| 2026-07-10 | DAL156 | JFK → ACC | Jul 10, 21:12 UTC | Jul 11, 06:52 UTC | 9h 40m |
| 2026-07-10 | DAL156 | - | Jul 10, 21:15 UTC | Jul 11, 03:45 UTC | 6h 30m |
| 2026-07-10 | DAL226 | - | Jul 10, 00:35 UTC | Jul 10, 10:05 UTC | 9h 30m |
About Mode-S
A Mode-S transponder code (also called an "ICAO 24-bit address" or "hex code") is a 6-character hexadecimal identifier permanently assigned to an aircraft when it's first registered. Unlike callsigns (which change with each flight) or registrations (which can change if an aircraft is sold internationally), the Mode-S address stays with the airframe for the life of the aircraft in that country.
Every ADS-B transmission from an aircraft includes its Mode-S address, making it the most reliable way to identify a specific airframe. Flight-tracking services like Apparatus use the Mode-S address as the primary key for tying position broadcasts, callsigns, and ownership records together.
Prefer a tail-number view? See the N421DX page for operator, model, and routing details .