Route reliability record
STL→DTW
St. Louis to Detroit
- Flights
- 1,905
- Period
- July 2025 to June 2026
- Distance
- 440 mi
- Carriers
- 5
This route lands a B, 4 points better than the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 1,905 STL to DTW flights, of which Delta Air Lines flew 1,088 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 92.4% of the time and Tuesday flights 87.1%, against 81.8% for the route overall.
Set against the rest of the country, this route's record is 4 points better than the US average of 77.6%. That gap is worth roughly 42 fewer late arrivals for every thousand flights.
Key figures
On time
81.8%
Arrivals under 15 minutes late, of 1,881 completed flights
Avg delay
87 min
Across delayed arrivals only, not all flights
Cancelled
1.15%
National rate is 1.81%
Best carrier
Delta
88.2% on time across 1,088 flights
These figures cover 1,905 flights between July 2025 and June 2026. The median arrival is 10 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.
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 73.6%. Sample sizes sit next to every figure, because a two-point gap across 593 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,088 | 88.2% | 102 min | 1.65% | A |
| Spirit Airlinesthin sample | 36 | 83.3% | 206 min | 0.00% | B+ |
| Southwest Airlines | 593 | 73.6% | 62 min | 0.34% | C+ |
| SkyWest Airlinesthin sample | 186 | 71.7% | 110 min | 1.08% | C |
| Republic Airwaysthin sample | 2 | 0.0% | 37 min | 0.00% | F+ |
The spread between Delta and Southwest is 15 points, wide enough that it should decide the booking. On a hundred trips that is 15 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.
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 | 86.7% | 88.2% | 1.65% | 5am–8am, Thu | DL 1626 06:40 |
| 2. STL → DTWSt. Louis to Detroit | Southwest Airlines | 73.3% | 73.6% | 0.34% | 8am–11am, Tue | — |
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 40 points, against 15 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am377 flights92.4%
- 8am–11am530 flights84.8%
- 11am–2pm112 flights81.2%
- 2pm–5pm180 flights79.2%
- 5pm–8pm600 flights78.7%
- 8pm–5am106 flights52.4%
Scale runs 45% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 52.4% on time, against 92.4% 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 600 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 22 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.
June is the worst month at 71.9% on time, 22 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. July was the busiest month here, with 188 flights.
Across the week, Tuesday is the strongest day at 87.1% on time and Monday the weakest at 75.4%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Carrier accounts for 46% of the 30,000 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.
- 46%Carrier
- 39%Late-arriving aircraft
- 9%Extreme weather
- 6%National Airspace System
39% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 30,000 reported delay minutes here, that single category outweighs weather by 5 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 29,619 reported delay minutes.
The largest share of delay minutes, 46%, 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 14,000 of the 30,000 delay minutes reported here.
Cancellations sit at 1.15% against a national 1.81%, which is ordinary. Diversions add another 0.10%.
Connections and stage length
What a delay here actually costs
7.9% 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 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 77.0% on time across 1,905 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 1,905 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 June 71.9%, a swing of 22 points. If the dates move at all, move them out of June before you think about anything else. 1,881 completed flights over 12 months sit behind that.
Common questions
STL to DTW questions
How often is STL to DTW delayed?
Roughly 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 18.2% of the 1,905 flights in this analysis, against 22.4% 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 1,088 flights. Southwest Airlines is at the other end on 73.6%, a gap of 15 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 92.4% on time. The 8pm–5am window is the weakest at 52.4%, 40 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 June delays on STL to DTW?
June is the weakest month at 71.9% on time, compared with 93.9% in September. Across the year that is 22 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 DTW73.6%
- SkyWest Airlines on STL to DTW71.7%
- STL to ATL, a related route85.3%
- ORD to DTW, a related route70.6%
- STL to DEN, a related route74.9%
- Delta Air Lines on-time record88.2%
- Spirit Airlines on-time record83.3%
- Southwest Airlines on-time record73.6%
- 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.