Flight number record
DL 1231
Delta Air Lines · New York to Detroit
- Route
- LGA → DTW
- Departs
- 06:00
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1231, check with Delta Air Lines.
DL 1231 earns an A−. Nearly every flight arrives inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 18 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 365 flights, with a median arrival 13 minutes early.
Set against the rest of the country, DL 1231's record is 18 points better than the US average of 77.3%. That gap is worth roughly 183 fewer late arrivals for every thousand flights.
Key figures
On time
95.6%
Arrivals under 15 minutes late, of 343 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
6.03%
National rate is 1.89%
1 hour+ late
1.5%
National rate is 8.3%
These figures cover 365 flights between September 2025 and August 2026. The median arrival is 13 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 1231 flies
DL 1231 flies LGA to DTW without a single fixed slot. Its most common scheduled departure was 06:00, used on 264 of 365 flights, with 06:05 (96 flights) next.
- Departs 06:00264 flights72.3%
- Departs 06:0596 flights26.3%
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 1231 runs 6 points better at 95.6%. 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 1231 next to LGA to DTW
Every carrier on LGA to DTW combined arrived on time 77.3% of the time across 3,861 flights, so DL 1231 is 18 points ahead of it. Delta flew 1,982 flights on the same city pair under all its flight numbers, including this one, and those ran 81.0% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 15 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 1231 | 365 | 95.6% | 58 min | 6.03% | A− |
| All Delta Air Lines on LGA–DTW | 1,982 | 81.0% | 87 min | 4.09% | B− |
| All carriers on LGA–DTW | 3,861 | 77.3% | 83 min | 5.23% | B− |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 1231 quarter by quarter
Quarter by quarter DL 1231 held fairly steady: 100.0% in Jul–Sep 2025, 90.6% in Oct–Dec 2025, 96.2% in Jan–Mar 2026, 100.0% in Apr–Jun 2026 and 93.1% 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 202592 flights90.6%
- Jan–Mar 202690 flights96.2%
- Apr–Jun 202691 flights100.0%
- Jul–Sep 202662 flights93.1%
Scale runs 80% to 100%.
By weekday, DL 1231 ranged from 91.3% on Monday to 98.0% on Wednesday. With about 52 flights behind each day, a spread of 7 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late DL 1231 runs when it is late
DL 1231 often beats the schedule: 157 of 343 completed flights, 46%, arrived 15 minutes or more early. The 15 late arrivals split 4 under half an hour, 6 between 30 and 60 minutes, and 5 an hour or more.
- 15+ min early157 flights45.8%
- Within 15 min171 flights49.9%
- 15–29 min late4 flights1.2%
- 30–59 min late6 flights1.7%
- 1–2 hours late3 flights0.9%
- 2+ hours late2 flights0.6%
Scale runs 0% to 100%.
Share of 343 completed flights by arrival against schedule.
Only 8 of 343 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 1231
The latest arrival of the period was on 20 July 2026, 2 hours 52 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 20 July 2026 | 2 hours 52 minutes | Carrier |
| 25 February 2026 | 2 hours 9 minutes | National Airspace System |
| 5 December 2025 | 1 hour 51 minutes | National Airspace System |
| 1 January 2026 | 1 hour 36 minutes | Carrier |
| 16 December 2025 | 1 hour 3 minutes | Carrier |
Delay causes
Why DL 1231 runs late
National Airspace System accounts for 59% of the 865 delay minutes carriers reported here, and the remaining four split what is left.
- 59%National Airspace System
- 42%Carrier
59% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 506 minutes out of 865, against a national NAS share of 21%. The split is drawn from 865 delay minutes reported on DL 1231.
Cancellations run at 6.03%, against 1.89% nationally. That is roughly one flight in fifteen 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 1.5% 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 502 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
Every one of the 365 flights under DL 1231 in the data flew LGA to DTW. The number was not reused on any other city pair, which makes this a clean record of one route.
One caution: this is a thin sample. 365 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 1231
For a booking, the cancellation rate is the figure to plan around on DL 1231: 6.03% of its 365 scheduled flights did not operate. A late arrival costs about an hour, but a cancellation costs the day, so leave a later option open.
Related
Where to go next
- LGA to DTW, every carrier and departure
- DTW to LGA, the return direction
- Delta Air Lines 1078 on the same route88.1%
- Delta Air Lines 1122 on the same route79.8%
- Delta Air Lines 999 on the same route73.9%
- Republic Airways 4598 on the same route63.6%
- Delta Air Lines 1014 on the same route69.3%
- LaGuardia (LGA) delay statistics
- Detroit Metropolitan Wayne County (DTW) 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.