Flight number record

DL 1240

Delta Air Lines · Atlanta to Detroit

Route: ATL → DTW
Departs: 11:00
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 365 flights, with a median arrival 5 minutes early.

Set against the rest of the country, DL 1240's record is 5 points better than the US average of 77.6%. That gap is worth roughly 54 fewer late arrivals for every thousand flights.

On time

83.0%

Arrivals under 15 minutes late, of 364 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.27%

National rate is 1.81%

1 hour+ late

5.5%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 2026. The median arrival is 5 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.

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 268 of 365 flights. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 11:00268 flights73.4%

Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.

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 78.8%, and DL 1240 runs 4 points better at 83.0%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

DL 1240 next to ATL to DTW

Every carrier on ATL to DTW combined arrived on time 78.0% of the time across 4,871 flights, so DL 1240 is 5 points ahead of it. Delta flew 3,698 flights on the same city pair under all its flight numbers, including this one, and those ran 79.5% on time. Across its whole network Delta Air Lines managed 81.6%, close to this flight's figure.

DL 1240 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 1240	365	83.0%	56 min	0.27%	B+
All Delta Air Lines on ATL–DTW	3,698	79.5%	57 min	0.51%	B+
All carriers on ATL–DTW	4,871	78.0%	63 min	0.82%	B+
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 1240 quarter by quarter

Quarter by quarter DL 1240 held fairly steady: 84.8% in Jul–Sep 2025, 83.5% in Oct–Dec 2025, 77.8% in Jan–Mar 2026 and 85.7% in Apr–Jun 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 202592 flights84.8%
Oct–Dec 202592 flights83.5%
Jan–Mar 202690 flights77.8%
Apr–Jun 202691 flights85.7%

Scale runs 70% to 90%. Rows with fewer than 30 flights show a dash.

By weekday, DL 1240 did best on Monday at 90.4% on time and worst on Sunday at 76.5%. Each day rests on about 52 flights, so a gap of 14 points is worth noticing but could still narrow in another year.

Delay causes

Why DL 1240 runs late

One category carries most of the weight here. Carrier accounts for 59% of the 3,498 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Carrier
59%
Late-arriving aircraft
28%
National Airspace System
10%
Extreme weather
3%

The largest share of delay minutes, 59%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 2,063 of the 3,498 delay minutes reported here. The split is drawn from 3,498 delay minutes reported on DL 1240.

Cancellations are rare at 0.27%, below the national 1.81% 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

5.5% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.

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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

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 83.0% on time with 0.27% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular day.

Where to go next

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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures