Route reliability record
STL→PHX
St. Louis to Phoenix
- Flights
- 2,309
- Period
- September 2025 to August 2026
- Distance
- 1,262 mi
- Carriers
- 5
This route sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 2,309 STL to PHX flights, of which American Airlines flew 584 at 81.5% on time.
Best time to fly STL to PHX: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 90.6% of the time and Tuesday flights 80.3%, against 74.8% 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
74.8%
Arrivals under 15 minutes late, of 2,290 completed flights
Avg delay
77 min
Across delayed arrivals only, not all flights
Cancelled
0.52%
National rate is 1.89%
Best carrier
American
81.5% on time across 584 flights
These figures cover 2,309 flights between September 2025 and August 2026. Beyond the headline rate, 8.5% 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 PHX
The choice of carrier is not cosmetic here. American Airlines arrives on time 81.5% of the time; Southwest Airlines manages 71.3%. Sample sizes sit next to every figure, because a two-point gap across 1,619 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Airthin sample | 30 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlinesthin sample | 23 | 95.7% | 211 min | 0.00% | A+ |
| Frontier Airlinesthin sample | 53 | 82.7% | 210 min | 1.89% | B |
| American Airlines | 584 | 81.5% | 174 min | 1.03% | B |
| Southwest Airlines | 1,619 | 71.3% | 52 min | 0.31% | C+ |
American leads Southwest by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on STL to PHX
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 Phoenix
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 → PHXSt. Louis to Phoenix | American Airlines | 80.7% | 81.5% | 1.03% | 8am–11am, Sat | AA 2574 08:00 |
| 2. STL → PHXSt. Louis to Phoenix | Southwest Airlines | 71.1% | 71.3% | 0.31% | 5am–8am, 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 38 points, against 10 points between the best and worst carrier.
- 5am–8am459 flights90.6%
- 8am–11am478 flights89.0%
- 11am–2pm205 flights75.4%
- 2pm–5pm478 flights74.0%
- 5pm–8pm347 flights56.4%
- 8pm–5am342 flights52.8%
Scale runs 45% to 95%.
The 8pm–5am window is where this operation falls apart: 52.8% on time, against 90.6% 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 8am–11am window is the busiest, with 478 flights scheduled in it.
Explore
Filter STL to PHX 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 PHX, the best departure window is 5am–8am at 90.6% on time and the worst is 8pm–5am at 52.8%, a wide gap of 37.8 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am90.6%
- 8–11am89.0%
- 11am–2pm75.4%
- 2–5pm74.0%
- 5–8pm56.4%
- 8pm–5am52.8%
best all US flightsScale 45% to 95%.
Across the year
When delays peak on this route
This route's year swings by 27 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 57.6% on time, 27 points below January, the best at 84.5%. 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. March was the busiest month here, with 233 flights.
Across the week, Tuesday is the strongest day at 80.3% on time and Sunday the weakest at 68.6%, a spread of 12 points.
Delay causes
Why this route gets delayed
Carrier accounts for 47% of the 45,000 delay minutes carriers reported here, and the remaining four split what is left.
- 47%Carrier
- 41%Late-arriving aircraft
- 10%National Airspace System
- 2%Extreme weather
- 0%Security
41% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 45,000 reported delay minutes here, that single category outweighs weather by 21 to one. The split is drawn from 44,514 reported delay minutes.
The largest share of delay minutes, 47%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 21,000 of the 45,000 delay minutes reported here.
Cancellations are rare at 0.52%, 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 stage length
What a delay here actually costs
8.5% 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 a little over an hour, which a normal layover absorbs.
The 1,262 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.
The return leg runs 76.2% on time across 2,323 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 2,309 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 PHX 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. January runs 84.5% on time and June 57.6%, a swing of 27 points. If the dates move at all, move them out of June before you think about anything else. 2,290 completed flights over 12 months sit behind that.
Common questions
STL to PHX questions
How often is STL to PHX delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 25.2% of the 2,309 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on STL to PHX?
American Airlines leads at 81.5% on time across 584 flights. Southwest Airlines is at the other end on 71.3%, a gap of 10 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 PHX?
The 5am–8am departure window is the strongest at 90.6% on time. The 8pm–5am window is the weakest at 52.8%, 38 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 PHX?
June is the weakest month at 57.6% on time, compared with 84.5% in January. Across the year that is 27 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
- PHX to STL — the return legseparate record
- St. Louis Lambert International (STL) delay statistics
- Phoenix Sky Harbor International (PHX) delay statistics
- American Airlines on STL to PHX81.5%
- Southwest Airlines on STL to PHX71.3%
- STL to DEN, a related route75.0%
- DEN to PHX, a related route75.6%
- STL to ATL, a related route84.6%
- Envoy Air on-time record100.0%
- SkyWest Airlines on-time record95.7%
- Frontier Airlines on-time record82.7%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. STL to PHX and PHX 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.