Flight number record

DL 1237

Delta Air Lines · Sioux Falls to Atlanta

Route: FSD → ATL
Departs: 05:20
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 77.6%. When something does go wrong the average delay runs close to two hours. That rests on 365 flights, with a median arrival 12 minutes early.

Set against the rest of the country, DL 1237's record is 9 points better than the US average of 77.6%. That gap is worth roughly 87 fewer late arrivals for every thousand flights.

On time

86.3%

Arrivals under 15 minutes late, of 358 completed flights

Avg delay

106 min

Across delayed arrivals only, not all flights

Cancelled

0.82%

National rate is 1.81%

1 hour+ late

6.1%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 2026. The median arrival is 12 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 1237 flies

DL 1237 flies FSD to ATL without a single fixed slot. Its most common scheduled departure was 05:20, used on 75 of 365 flights, with 05:30 (59 flights) and 05:15 (40 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 05:2075 flights20.5%
Departs 05:3059 flights16.2%
Departs 05:1540 flights11.0%

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 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 86.3%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

DL 1237 next to FSD to ATL

Across its whole network Delta Air Lines managed 81.6%, which this flight beats by 5 points.

DL 1237 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
DL 1237	365	86.3%	106 min	0.82%	A+
All Delta Air Lines on FSD–ATL	365	86.3%	106 min	0.82%	A+
All carriers on FSD–ATL	365	86.3%	106 min	0.82%	A+
Delta Air Lines, whole network	1,038,570	81.6%	71 min	1.62%	B

Across the year

DL 1237 quarter by quarter

DL 1237 did not run the same all year. Its best quarter was Apr–Jun 2026 at 92.1% on time and its weakest Oct–Dec 2025 at 73.9%, a swing of 18 points on roughly 91 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 202592 flights91.3%
Oct–Dec 202592 flights73.9%
Jan–Mar 202690 flights87.6%
Apr–Jun 202691 flights92.1%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

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.

Delay causes

Why DL 1237 runs late

One category carries most of the weight here. Carrier accounts for 66% of the 5,194 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
66%
Extreme weather
14%
National Airspace System
13%
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 2.2 times the usual weather exposure. The split is drawn from 5,194 delay minutes reported on DL 1237.

Cancellations are rare at 0.82%, 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

6.1% 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 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. 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 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: 86.3% 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures