Route reliability record
PHX→BOI
Phoenix to Boise
- Flights
- 1,986
- Period
- July 2025 to June 2026
- Distance
- 735 mi
- Carriers
- 5
This route lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about 55 minutes on average. That is a workable record, not a spotless one. That rests on 1,986 PHX to BOI flights, of which SkyWest Airlines flew 1,001 at 84.0% on time.
Best time to fly PHX to BOI: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 96.7% of the time and Saturday flights 84.1%, against 80.4% for the route overall.
The US average over the same twelve months is 77.6%, 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
80.4%
Arrivals under 15 minutes late, of 1,974 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.40%
National rate is 1.81%
Best carrier
SkyWest
84.0% on time across 1,001 flights
These figures cover 1,986 flights between July 2025 and June 2026. The median arrival is 5 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 PHX to BOI
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 84.0% of the time; Southwest Airlines manages 77.3%. Sample sizes sit next to every figure, because a two-point gap across 813 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlinesthin sample | 5 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,001 | 84.0% | 69 min | 0.60% | B+ |
| Southwest Airlines | 813 | 77.3% | 45 min | 0.25% | B+ |
| Envoy Airthin sample | 115 | 77.2% | 34 min | 0.00% | B+ |
| American Airlinesthin sample | 52 | 67.3% | 60 min | 0.00% | C+ |
SkyWest leads Southwest by 7 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Best ways to make this trip
The most reliable ways to fly Phoenix to Boise
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. PHX → BOIPhoenix to Boise | SkyWest Airlines | 83.5% | 84.0% | 0.60% | 11am–2pm, Mon | — |
| 2. PHX → BOIPhoenix to Boise | Southwest Airlines | 77.1% | 77.3% | 0.25% | 8am–11am, Sat | — |
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 31 points, against 7 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am30 flights96.7%
- 8am–11am691 flights83.7%
- 11am–2pm302 flights82.9%
- 2pm–5pm431 flights84.0%
- 5pm–8pm132 flights65.6%
- 8pm–5am400 flights72.8%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 96.7% of the time, against 65.6% for the evening window. That is 31 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 691 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 16 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 70.2% on time, 16 points below August, the best at 86.6%. 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. October was the busiest month here, with 198 flights.
Across the week, Saturday is the strongest day at 84.1% on time and Sunday the weakest at 77.7%. 6 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 21,000 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
- 8%Extreme weather
- 8%National Airspace System
- 0%Security
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 21,000 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 21,115 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 9,626 of the 21,000 delay minutes reported here.
Cancellations are rare at 0.40%, 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 stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.6% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The 735 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.
The return leg is a different operation and performs like one: it runs 83.9% on time across 1,985 flights, 4 points above 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 4 points of difference.
The sample behind these figures is 1,986 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 BOI 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. August runs 86.6% on time and June 70.2%, a swing of 16 points. If the dates move at all, move them out of June before you think about anything else. 1,974 completed flights over 12 months sit behind that.
Common questions
PHX to BOI questions
How often is PHX to BOI 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 19.6% of the 1,986 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 55 minutes on average.
Which airline is most reliable on PHX to BOI?
SkyWest Airlines leads at 84.0% on time across 1,001 flights. Southwest Airlines is at the other end on 77.3%, a gap of 7 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 PHX to BOI?
The 5am–8am departure window is the strongest at 96.7% on time. The 5pm–8pm window is the weakest at 65.6%, 31 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 PHX to BOI?
June is the weakest month at 70.2% on time, compared with 86.6% in August. Across the year that is 16 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
- BOI to PHX — the return legseparate record
- Phoenix Sky Harbor International (PHX) delay statistics
- SkyWest Airlines on PHX to BOI84.0%
- Southwest Airlines on PHX to BOI77.3%
- Envoy Air on PHX to BOI77.2%
- PHX to DEN, a related route77.2%
- SEA to BOI, a related route85.8%
- PHX to LAX, a related route82.8%
- Alaska Airlines on-time record100.0%
- SkyWest Airlines on-time record84.0%
- Southwest Airlines on-time record77.3%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. PHX to BOI and BOI to PHX 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.