Flight number record
DL 1721
Delta Air Lines · Mobile to Atlanta
- Route
- MOB → ATL
- Departs
- 06:00
- Flights
- 277
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1721, check with Delta Air Lines.
DL 1721 earns an A. Nearly every flight arrives inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 16 points better than the national rate of 77.3%. When something does go wrong the average delay runs about 2.4 hours. That rests on 277 flights, with a median arrival 17 minutes early.
Set against the rest of the country, DL 1721's record is 16 points better than the US average of 77.3%. That gap is worth roughly 160 fewer late arrivals for every thousand flights.
Key figures
On time
93.3%
Arrivals under 15 minutes late, of 269 completed flights
Avg delay
146 min
Across delayed arrivals only, not all flights
Cancelled
2.89%
National rate is 1.89%
1 hour+ late
4.1%
National rate is 8.3%
These figures cover 277 flights between September 2025 and August 2026. The median arrival is 17 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
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Schedule
When DL 1721 flies
DL 1721 flies MOB to ATL without a single fixed slot. Its most common scheduled departure was 06:00, used on 150 of 277 flights, with 06:05 (57 flights) and 06:15 (36 flights) next.
- Departs 06:00150 flights54.2%
- Departs 06:0557 flights20.6%
- Departs 06:1536 flights13.0%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 06:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and DL 1721 runs 4 points better at 93.3%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
DL 1721 next to MOB to ATL
Every carrier on MOB to ATL combined arrived on time 83.3% of the time across 926 flights, so DL 1721 is 10 points ahead of it. Delta flew 780 flights on the same city pair under all its flight numbers, including this one, and those ran 85.2% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 12 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 1721thin sample | 277 | 93.3% | 146 min | 2.89% | A |
| All Delta Air Lines on MOB–ATL | 780 | 85.2% | 90 min | 2.18% | A |
| All carriers on MOB–ATL | 926 | 83.3% | 93 min | 2.05% | B |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 1721 quarter by quarter
Quarter by quarter DL 1721 held fairly steady: 100.0% in Jul–Sep 2025, 97.4% in Oct–Dec 2025, 91.5% in Jan–Mar 2026, 91.1% in Apr–Jun 2026 and 91.9% in Jul–Sep 2026. A spread of 9 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202530 flights100.0%
- Oct–Dec 202539 flights97.4%
- Jan–Mar 202686 flights91.5%
- Apr–Jun 202660 flights91.1%
- Jul–Sep 202662 flights91.9%
Scale runs 85% to 100%.
By weekday, DL 1721 did best on Friday at 100.0% on time and worst on Monday at 82.1%. Each day rests on about 40 flights, so a gap of 18 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late DL 1721 runs when it is late
DL 1721 often beats the schedule: 155 of 269 completed flights, 58%, arrived 15 minutes or more early. When DL 1721 is late it tends to be very late: 11 of its 18 late arrivals were an hour or more behind, and 7 were two hours or more.
- 15+ min early155 flights57.6%
- Within 15 min96 flights35.7%
- 15–29 min late4 flights1.5%
- 30–59 min late3 flights1.1%
- 1–2 hours late4 flights1.5%
- 2+ hours late7 flights2.6%
Scale runs 0% to 100%.
Share of 269 completed flights by arrival against schedule.
Only 16 of 269 completed flights left 15 minutes late or more, too few to say how often the time is made up.
The worst days
Worst days for DL 1721
The latest arrival of the period was on 23 August 2026, 9 hours 28 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 23 August 2026 | 9 hours 28 minutes | Carrier |
| 3 March 2026 | 7 hours 12 minutes | Carrier |
| 15 June 2026 | 3 hours 58 minutes | Carrier |
| 28 February 2026 | 3 hours 54 minutes | Late-arriving aircraft |
| 12 August 2026 | 3 hours 30 minutes | Carrier |
Delay causes
Why DL 1721 runs late
Carrier accounts for 77% of the 2,622 delay minutes carriers reported here, and the remaining four split what is left.
- 77%Carrier
- 13%Late-arriving aircraft
- 7%National Airspace System
- 3%Extreme weather
The largest share of delay minutes, 77%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,013 of the 2,622 delay minutes reported here. The split is drawn from 2,622 delay minutes reported on DL 1721.
Cancellations run at 2.89%, against 1.89% nationally. That is roughly one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 4.1% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The same number turns up on two other city pairs in the data, including SJU to BOS (16) and BOS to LGA (1), but none flew often enough under DL 1721 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to MOB to ATL only.
One caution: this is a thin sample. 277 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking DL 1721
For a booking, the cancellation rate is the figure to plan around on DL 1721: 2.89% of its 277 scheduled flights did not operate. A late arrival costs about 2.4 hours, but a cancellation costs the day, so leave a later option open.
Related
Where to go next
- MOB to ATL, every carrier and departure
- ATL to MOB, the return direction
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Delta Air Lines on-time record
- Every Delta Air Lines flight number with a record
- The most and least reliable flight numbers in the US
- What a cancellation rate actually tells you (and what it hides)
A flight number here means Delta Air Lines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.