Flight number record

DL 1237

Delta Air Lines · Sioux Falls to Atlanta

Route: FSD → ATL
Departs: 05:20
Flights: 365
Period: September 2025 to August 2026

Historical statistics for September 2025 to August 2026, not live status. For today’s DL 1237, check with Delta Air Lines.

DL 1237 earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.3%. When something does go wrong the average delay runs close to two hours. That rests on 365 flights, with a median arrival 13 minutes early.

Set against the rest of the country, DL 1237's record is 9 points better than the US average of 77.3%. That gap is worth roughly 93 fewer late arrivals for every thousand flights.

On time

86.6%

Arrivals under 15 minutes late, of 358 completed flights

Avg delay

111 min

Across delayed arrivals only, not all flights

Cancelled

0.82%

National rate is 1.89%

1 hour+ late

6.7%

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 1237 flies

DL 1237 flies FSD to ATL without a single fixed slot. Its most common scheduled departure was 05:20, used on 108 of 365 flights, with 05:30 (84 flights) and 05:05 (39 flights) next.

Departs 05:20108 flights29.6%
Departs 05:3084 flights23.0%
Departs 05:0539 flights10.7%

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 05:20 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and DL 1237 runs 3 points worse at 86.6%. 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 1237 next to FSD to ATL

Across its whole network Delta Air Lines managed 81.1%, which this flight beats by 6 points.

DL 1237 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 1237	365	86.6%	111 min	0.82%	A+
All Delta Air Lines on FSD–ATL	365	86.6%	111 min	0.82%	A+
All carriers on FSD–ATL	365	86.6%	111 min	0.82%	A+
Delta Air Lines, whole network	1,039,517	81.1%	71 min	1.74%	B

Across the year

DL 1237 quarter by quarter

DL 1237 did not run the same all year. Its best quarter was Jul–Sep 2025 at 93.3% on time and its weakest Oct–Dec 2025 at 73.9%, a swing of 19 points on roughly 73 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Jul–Sep 202530 flights93.3%
Oct–Dec 202592 flights73.9%
Jan–Mar 202690 flights87.6%
Apr–Jun 202691 flights92.1%
Jul–Sep 202662 flights91.9%

Scale runs 65% to 100%.

By weekday, DL 1237 ranged from 82.7% on Saturday to 90.4% on Thursday. With about 52 flights behind each day, a spread of 8 points is inside normal variation, so the day you fly is not worth changing for this flight.

Arrival by arrival

How late DL 1237 runs when it is late

DL 1237 often beats the schedule: 163 of 358 completed flights, 46%, arrived 15 minutes or more early. The 48 late arrivals split 17 under half an hour, 7 between 30 and 60 minutes, and 24 an hour or more.

15+ min early163 flights45.5%
Within 15 min147 flights41.1%
15–29 min late17 flights4.7%
30–59 min late7 flights2.0%
1–2 hours late10 flights2.8%
2+ hours late14 flights3.9%

Scale runs 0% to 100%.

Share of 358 completed flights by arrival against schedule.

7 of 37 late departures made up the time and arrived on time, 19% of them. In the other direction, 18 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at ATL.

The worst days

Worst days for DL 1237

The latest arrival of the period was on 21 February 2026, 8 hours 26 minutes behind schedule; most of its delay minutes were filed as extreme weather. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).

The latest arrivals of DL 1237 in the period
Date	Arrived late by	Largest filed cause
21 February 2026	8 hours 26 minutes	Extreme weather
30 November 2025	8 hours 14 minutes	Carrier
24 December 2025	7 hours 52 minutes	Carrier
18 January 2026	6 hours 25 minutes	Carrier
20 May 2026	5 hours 54 minutes	Late-arriving aircraft

Delay causes

Why DL 1237 runs late

Carrier accounts for 68% of the 5,318 delay minutes carriers reported here, and the remaining four split what is left.

Carrier
68%
Extreme weather
14%
National Airspace System
11%
Late-arriving aircraft
7%

Extreme weather accounts for 14% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.3 times the usual weather exposure. The split is drawn from 5,318 delay minutes reported on DL 1237.

Cancellations are rare at 0.82%, 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

6.7% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last close to two hours, which a normal layover absorbs.

The 954 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 1237 in the data flew FSD to ATL. 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 1237

For a booking, DL 1237 has one of the better records a US domestic flight can show: 86.6% on time and 0.82% cancelled. That is a base rate, not a promise about any single 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, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures