Route reliability record
STL→DTW
St. Louis to Detroit
- Flights
- 1,899
- Period
- September 2025 to August 2026
- Distance
- 440 mi
- Carriers
- 4
This route lands a B, 4 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That rests on 1,899 STL to DTW flights, of which Delta Air Lines flew 1,104 at 88.2% on time.
Best time to fly STL to DTW: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 91.8% of the time and Tuesday flights 85.7%, against 81.1% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
81.1%
Arrivals under 15 minutes late, of 1,874 completed flights
Avg delay
85 min
Across delayed arrivals only, not all flights
Cancelled
1.21%
National rate is 1.89%
Best carrier
Delta
88.2% on time across 1,104 flights
These figures cover 1,899 flights between September 2025 and August 2026. Beyond the headline rate, 8.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on STL to DTW
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 88.2% of the time; Southwest Airlines manages 71.5%. Sample sizes sit next to every figure, because a two-point gap across 611 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Delta Air Lines | 1,104 | 88.2% | 111 min | 1.81% | A |
| Southwest Airlines | 611 | 71.5% | 59 min | 0.16% | C+ |
| SkyWest Airlinesthin sample | 183 | 71.3% | 110 min | 1.09% | C |
The spread between Delta and Southwest is 17 points, wide enough that it should decide the booking. On a hundred trips that is 17 more arrivals inside the on-time window.
Flight by flight
Flights on STL to DTW
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly St. Louis to Detroit
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. STL → DTWSt. Louis to Detroit | Delta Air Lines | 86.6% | 88.2% | 1.81% | 5am–8am, Wed | DL 1626 06:40 |
| 2. STL → DTWSt. Louis to Detroit | Southwest Airlines | 71.4% | 71.5% | 0.16% | 8am–11am, Fri | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 32 points, against 17 points between the best and worst carrier.
- 5am–8am377 flights91.8%
- 8am–11am523 flights83.6%
- 11am–2pm108 flights83.3%
- 2pm–5pm187 flights78.9%
- 5pm–8pm593 flights76.6%
- 8pm–5am111 flights59.5%
Scale runs 50% to 95%.
The 8pm–5am window is where this operation falls apart: 59.5% on time, against 91.8% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5pm–8pm window is the busiest, with 593 flights scheduled in it.
Explore
Filter STL to DTW by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On STL to DTW, the best departure window is 5am–8am at 91.8% on time and the worst is 8pm–5am at 59.5%, a wide gap of 32.3 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am91.8%
- 8–11am83.6%
- 11am–2pm83.3%
- 2–5pm78.9%
- 5–8pm76.6%
- 8pm–5am59.5%
best all US flightsScale 50% to 95%.
Across the year
When delays peak on this route
This route's year swings by 24 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 70.3% on time, 24 points below September, the best at 93.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. August was the busiest month here, with 180 flights.
Across the week, Tuesday is the strongest day at 85.7% on time and Monday the weakest at 75.6%, a spread of 10 points.
Delay causes
Why this route gets delayed
Carrier accounts for 50% of the 30,000 delay minutes carriers reported here, and the remaining four split what is left.
- 50%Carrier
- 37%Late-arriving aircraft
- 7%National Airspace System
- 6%Extreme weather
- 0%Security
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 30,000 reported delay minutes here, that single category outweighs weather by 6 to one. The split is drawn from 30,168 reported delay minutes.
The largest share of delay minutes, 50%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 15,000 of the 30,000 delay minutes reported here.
Cancellations sit at 1.21% against a national 1.89%, which is ordinary. Diversions add another 0.11%.
Connections and stage length
What a delay here actually costs
8.0% 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 an hour and a half, which a normal layover absorbs.
At 440 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 76.6% on time across 1,899 flights, 5 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 5 points of difference.
The sample behind these figures is 1,899 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in DTW after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 93.9% on time and July 70.3%, a swing of 24 points. If the dates move at all, move them out of July before you think about anything else. 1,874 completed flights over 12 months sit behind that.
Common questions
STL to DTW questions
How often is STL to DTW delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.9% of the 1,899 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on STL to DTW?
Delta Air Lines leads at 88.2% on time across 1,104 flights. Southwest Airlines is at the other end on 71.5%, a gap of 17 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on STL to DTW?
The 5am–8am departure window is the strongest at 91.8% on time. The 8pm–5am window is the weakest at 59.5%, 32 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on STL to DTW?
July is the weakest month at 70.3% on time, compared with 93.9% in September. Across the year that is 24 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DTW to STL — the return legseparate record
- St. Louis Lambert International (STL) delay statistics
- Detroit Metropolitan Wayne County (DTW) delay statistics
- Delta Air Lines on STL to DTW88.2%
- Southwest Airlines on STL to DTW71.5%
- SkyWest Airlines on STL to DTW71.3%
- STL to DEN, a related route75.0%
- ORD to DTW, a related route71.1%
- STL to ATL, a related route84.6%
- Spirit Airlines on-time record100.0%
- Delta Air Lines on-time record88.2%
- Southwest Airlines on-time record71.5%
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
Direction matters. STL to DTW and DTW to STL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.