Flight number record
DL 1240
Delta Air Lines · Atlanta to Detroit
- Route
- ATL → DTW
- Departs
- 11:00
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1240, check with Delta Air Lines.
DL 1240 lands a B+, 5 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about 50 minutes on average. That rests on 365 flights, with a median arrival 4 minutes early.
Set against the rest of the country, DL 1240's record is 5 points better than the US average of 77.3%. That gap is worth roughly 54 fewer late arrivals for every thousand flights.
Key figures
On time
82.7%
Arrivals under 15 minutes late, of 364 completed flights
Avg delay
51 min
Across delayed arrivals only, not all flights
Cancelled
0.27%
National rate is 1.89%
1 hour+ late
4.1%
National rate is 8.3%
These figures cover 365 flights between September 2025 and August 2026. The median arrival is 4 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 1240 flies
DL 1240 flies ATL to DTW without a single fixed slot. Its most common scheduled departure was 11:00, used on 273 of 365 flights.
- Departs 11:00273 flights74.8%
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 11:00 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.3%, and DL 1240 runs 4 points better at 82.7%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
DL 1240 next to ATL to DTW
Every carrier on ATL to DTW combined arrived on time 76.4% of the time across 4,821 flights, so DL 1240 is 6 points ahead of it. Delta flew 3,774 flights on the same city pair under all its flight numbers, including this one, and those ran 77.9% on time. Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 2 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| DL 1240 | 365 | 82.7% | 51 min | 0.27% | B+ |
| All Delta Air Lines on ATL–DTW | 3,774 | 77.9% | 60 min | 0.50% | B+ |
| All carriers on ATL–DTW | 4,821 | 76.4% | 64 min | 0.81% | B+ |
| Delta Air Lines, whole network | 1,039,517 | 81.1% | 71 min | 1.74% | B |
Across the year
DL 1240 quarter by quarter
Quarter by quarter DL 1240 held fairly steady: 83.3% in Jul–Sep 2025, 83.5% in Oct–Dec 2025, 77.8% in Jan–Mar 2026, 85.7% in Apr–Jun 2026 and 83.9% in Jul–Sep 2026. A spread of 8 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202530 flights83.3%
- Oct–Dec 202592 flights83.5%
- Jan–Mar 202690 flights77.8%
- Apr–Jun 202691 flights85.7%
- Jul–Sep 202662 flights83.9%
Scale runs 70% to 90%.
By weekday, DL 1240 ranged from 78.4% on Sunday to 88.5% on Wednesday. With about 52 flights behind each day, a spread of 10 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late DL 1240 runs when it is late
The 63 late arrivals split 31 under half an hour, 17 between 30 and 60 minutes, and 15 an hour or more.
- 15+ min early58 flights15.9%
- Within 15 min243 flights66.8%
- 15–29 min late31 flights8.5%
- 30–59 min late17 flights4.7%
- 1–2 hours late10 flights2.7%
- 2+ hours late5 flights1.4%
Scale runs 0% to 100%.
Share of 364 completed flights by arrival against schedule.
12 of 64 late departures made up the time and arrived on time, 19% of them. 11 flights left on time and still arrived late.
The worst days
Worst days for DL 1240
The latest arrival of the period was on 7 December 2025, 4 hours 53 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 7 December 2025 | 4 hours 53 minutes | Late-arriving aircraft |
| 17 January 2026 | 3 hours 31 minutes | Late-arriving aircraft |
| 31 October 2025 | 3 hours 7 minutes | Carrier |
| 11 June 2026 | 2 hours 48 minutes | Carrier |
| 16 March 2026 | 2 hours 36 minutes | Carrier |
Delay causes
Why DL 1240 runs late
Carrier accounts for 57% of the 3,212 delay minutes carriers reported here, and the remaining four split what is left.
- 57%Carrier
- 32%Late-arriving aircraft
- 11%National Airspace System
- 1%Extreme weather
The largest share of delay minutes, 57%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,828 of the 3,212 delay minutes reported here. The split is drawn from 3,212 delay minutes reported on DL 1240.
Cancellations are rare at 0.27%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
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 594 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 1240 in the data flew ATL 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 1240
For a booking, read DL 1240 as 82.7% on time with 0.27% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- ATL to DTW, every carrier and departure
- DTW to ATL, the return direction
- Delta Air Lines 1298 on the same route84.3%
- Delta Air Lines 1031 on the same route83.9%
- Delta Air Lines 1646 on the same route90.6%
- Delta Air Lines 1005 on the same route75.2%
- Delta Air Lines 2940 on the same route72.6%
- Delta Air Lines 2067 on the same route74.6%
- Hartsfield-Jackson Atlanta International (ATL) 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
- Worst months to fly in the US, ranked by the data
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.