Apparatus

Try JFK, AAL1290, BAW, or N225AN.

sensors Mode-S transponder

AB7A21

ICAO 24-bit transponder address · allocated to United States

Currently assigned to N839DN · BOEING 737-900 · operated by DELTA AIR LINES INC

Hex
AB7A21
Octal
52675041
Decimal
11,237,921
Country
US
Tail
N839DN
Type
B739
No current signal · last broadcast Jul 26, 22:15 UTC
Flights observed
536
Distinct callsigns
20
Country
US
Last broadcast
Jul 26, 22:15 UTC

Last known position

Most recent position reported by Mode-S AB7A21.

Country allocation

The ICAO 24-bit address AB7A21 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
DAL801 Delta Air Lines 6 2026-07-25
DAL2530 - 6 2026-07-14
DAL1757 Delta Air Lines 5 2026-07-24
DAL1421 Delta Air Lines 5 2026-06-03
DAL1244 - 5 2026-07-19
DAL1002 Delta Air Lines 5 2026-06-10
DAL858 Delta Air Lines 4 2026-05-30
DAL2988 - 4 2026-07-07
DAL2908 - 4 2026-07-15
DAL2879 Delta Air Lines 4 2026-05-05
DAL2752 Delta Air Lines 4 2026-05-18
DAL2674 Delta Air Lines 4 2026-05-22
DAL2669 - 4 2026-07-06
DAL2612 Delta Air Lines 4 2026-05-29
DAL2587 Delta Air Lines 4 2026-04-17
DAL2439 Delta Air Lines 4 2026-05-30
DAL2253 Delta Air Lines 4 2026-06-22
DAL2208 Delta Air Lines 4 2026-05-24
DAL2089 Delta Air Lines 4 2026-07-21
DAL967 - 3 2026-07-01

Recent flights last 50

DateFlightRouteTakeoffLandingDuration
2026-07-26 DAL809 SJC → ATL Jul 26, 20:20 UTCJul 26, 22:15 UTC1h 55m
2026-07-26 DAL809 SJC → ATL Jul 26, 14:15 UTCJul 26, 18:30 UTC4h 15m
2026-07-26 DAL1524 BOS → ORD Jul 26, 11:10 UTCJul 26, 12:25 UTC1h 15m
2026-07-26 DAL1403 RSW → MSP Jul 26, 02:55 UTCJul 26, 04:05 UTC1h 10m
2026-07-25 DAL1956 NAS → ATL Jul 25, 22:25 UTCJul 26, 00:00 UTC1h 35m
2026-07-25 DAL1947 ATL → NAS Jul 25, 19:01 UTCJul 25, 20:42 UTC1h 41m
2026-07-25 DAL1947 ATL → NAS Jul 25, 19:05 UTCJul 25, 20:20 UTC1h 15m
2026-07-25 DAL801 ATL → YUL Jul 25, 15:35 UTCJul 25, 16:55 UTC1h 20m
2026-07-25 DAL801 ATL → YUL Jul 25, 12:30 UTCJul 25, 14:00 UTC1h 30m
2026-07-25 DAL878 RDU → LGA Jul 25, 06:10 UTCJul 25, 10:15 UTC4h 5m
2026-07-25 DAL878 RDU → LGA Jul 25, 06:07 UTCJul 25, 10:16 UTC4h 9m
2026-07-24 DAL743 ATL → SMF Jul 24, 22:55 UTCJul 25, 03:55 UTC5h 0m
2026-07-24 DAL1757 SLC → SJD Jul 24, 20:05 UTCJul 24, 21:00 UTC55m
2026-07-24 DAL1757 SLC → SJD Jul 24, 17:45 UTCJul 24, 17:55 UTC10m
2026-07-24 DAL1757 SLC → SJD Jul 24, 17:42 UTCJul 24, 20:58 UTC3h 16m
2026-07-24 DAL1757 SLC → SJD Jul 24, 16:05 UTCJul 24, 16:15 UTC10m
2026-07-24 DAL1757 SLC → SJD Jul 24, 13:10 UTCJul 24, 14:20 UTC1h 10m
2026-07-24 DAL2966 RDU → LGA Jul 24, 09:25 UTCJul 24, 10:15 UTC50m
2026-07-24 DAL2966 RDU → LGA Jul 24, 09:22 UTCJul 24, 10:39 UTC1h 17m
2026-07-24 DAL2731 ATL → ORF Jul 24, 03:15 UTCJul 24, 04:30 UTC1h 15m
2026-07-23 DAL2714 BUF → BOS Jul 23, 23:10 UTCJul 24, 00:45 UTC1h 35m
2026-07-23 DAL1734 IAH → LGA Jul 23, 19:35 UTCJul 23, 21:25 UTC1h 50m
2026-07-23 DAL1029 DAY → ATL Jul 23, 16:05 UTCJul 23, 17:55 UTC1h 50m
2026-07-23 DAL2611 BOS → JFK Jul 23, 10:25 UTCJul 23, 11:10 UTC45m
2026-07-23 DAL2611 BOS → JFK Jul 23, 10:24 UTCJul 23, 11:10 UTC46m
2026-07-23 DAL2639 EWR → ATL Jul 23, 01:25 UTCJul 23, 02:10 UTC45m
2026-07-22 DAL2378 SMF → SEA Jul 22, 21:30 UTCJul 22, 23:20 UTC1h 50m
2026-07-22 DAL1359 PBI → LGA Jul 22, 19:10 UTCJul 22, 19:55 UTC45m
2026-07-22 DAL1359 PBI → LGA Jul 22, 17:25 UTCJul 22, 18:05 UTC40m
2026-07-22 DAL2161 TPA → JFK Jul 22, 14:55 UTCJul 22, 16:00 UTC1h 5m
2026-07-22 DAL2161 TPA → JFK Jul 22, 14:25 UTCJul 22, 14:50 UTC25m
2026-07-22 DAL2865 ATL → GRR Jul 22, 02:05 UTCJul 22, 03:35 UTC1h 30m
2026-07-21 DAL2329 ATL → PVD Jul 21, 22:30 UTCJul 21, 23:50 UTC1h 20m
2026-07-21 DAL2329 ATL → PVD Jul 21, 19:40 UTCJul 21, 20:50 UTC1h 10m
2026-07-21 DAL570 - Jul 21, 13:45 UTCJul 21, 18:00 UTC4h 15m
2026-07-21 DAL2089 BOS → BNA Jul 21, 03:25 UTCJul 21, 06:57 UTC3h 32m
2026-07-21 DAL2089 BOS → BNA Jul 21, 03:30 UTCJul 21, 07:05 UTC3h 35m
2026-07-20 DAL2946 MSP → DFW Jul 20, 18:35 UTCJul 20, 23:55 UTC5h 19m
2026-07-20 DAL2134 RIC → ATL Jul 20, 13:45 UTCJul 20, 17:00 UTC3h 15m
2026-07-20 DAL2134 RIC → ATL Jul 20, 13:44 UTCJul 20, 16:59 UTC3h 15m
2026-07-20 DAL2672 ATL → DTW Jul 20, 03:50 UTCJul 20, 06:15 UTC2h 25m
2026-07-19 DAL871 SLC → SEA Jul 19, 23:55 UTCJul 20, 01:30 UTC1h 35m
2026-07-19 DAL849 SFO → SLC Jul 19, 20:53 UTCJul 19, 22:13 UTC1h 20m
2026-07-19 DAL849 SFO → SLC Jul 19, 20:55 UTCJul 19, 22:15 UTC1h 20m
2026-07-19 DAL902 BOS → DEN Jul 19, 17:20 UTCJul 19, 19:00 UTC1h 40m
2026-07-19 DAL902 BOS → DEN Jul 19, 17:18 UTCJul 19, 18:56 UTC1h 38m
2026-07-19 DAL1176 BWI → SLC Jul 19, 11:30 UTCJul 19, 15:30 UTC4h 0m
2026-07-19 DAL2079 SLC → BWI Jul 19, 06:05 UTCJul 19, 09:45 UTC3h 40m
2026-07-19 DAL1244 - Jul 19, 00:25 UTCJul 19, 02:00 UTC1h 35m
2026-07-19 DAL1244 PDX → SLC Jul 19, 00:25 UTCJul 19, 01:48 UTC1h 23m

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 N839DN page for operator, model, and routing details .

Mode-S AB7A21 frequently asked

What is Mode-S code AB7A21?
AB7A21 is an ICAO 24-bit transponder address. Allocated to United States. Assigned to N839DN.
Where is Mode-S AB7A21 registered?
Mode-S code AB7A21 is allocated to United States (US). All aircraft registered there receive a Mode-S address from a fixed block defined by ICAO Annex 10.
Is AB7A21 broadcasting right now?
No active broadcast right now. Last signal was Jul 26, 22:15 UTC.
Hex, octal, and decimal Mode-S codes: what's the difference?
The same 24-bit identifier expressed in different bases: hex AB7A21, octal 52675041, decimal 11,237,921.
What flights does AB7A21 operate?
Mode-S AB7A21 has broadcast 20 distinct callsigns, including DAL801, DAL2530, DAL1757, DAL1421, DAL1244.