Route reliability record
PHL→SLC
Philadelphia to Salt Lake City
- Flights
- 833
- Period
- July 2025 to June 2026
- Distance
- 1,927 mi
- Carriers
- 2
This route lands a B, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 833 PHL to SLC flights, with a median arrival 2 minutes early.
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
76.9%
Arrivals under 15 minutes late, of 811 completed flights
Avg delay
67 min
Across delayed arrivals only, not all flights
Cancelled
2.40%
National rate is 1.81%
Best carrier
Delta
78.3% on time across 613 flights
These figures cover 833 flights between July 2025 and June 2026. The median arrival is 2 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 PHL to SLC
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 613 | 78.3% | 59 min | 1.31% | B |
| American Airlinesthin sample | 220 | 72.9% | 85 min | 5.45% | C− |
Flight by flight
Flights on PHL to SLC
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.
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 14 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am364 flights84.4%
- 8am–11am—
- 11am–2pm—
- 2pm–5pm3 flights—
- 5pm–8pm450 flights70.6%
- 8pm–5am16 flights—
Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 84.4% of the time, against 70.6% for the evening window. That is 14 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 450 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 40 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.
December is the weak month at 52.5% on time, against 92.0% in April. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 92 flights.
Across the week, Tuesday is the strongest day at 82.5% on time and Thursday the weakest at 71.4%. 11 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 43% of the 12,000 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.
- 43%Carrier
- 28%National Airspace System
- 25%Late-arriving aircraft
- 4%Extreme weather
The largest share of delay minutes, 43%, 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 5,337 of the 12,000 delay minutes reported here. The split is drawn from 12,485 reported delay minutes.
Cancellations sit at 2.40% against a national 1.81%, which is ordinary. Diversions add another 0.24%.
Connections and stage length
What a delay here actually costs
6.4% 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 about an hour, which a normal layover absorbs.
At 1,927 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 84.7% on time across 833 flights, 8 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 8 points of difference.
One caution: this is a thin sample. 833 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.
Work out the risk of missing a connection in SLC after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 833 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 76.9% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 811 completed flights over 12 months sit behind that.
Common questions
PHL to SLC questions
How often is PHL to SLC delayed?
Roughly 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 23.1% of the 833 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is PHL to SLC compared with the rest of the country?
76.9% of flights arrive on time here against a national 77.6%, a difference of half a point against it. That is worth a B on this site's grading scale.
What time of day has the fewest delays on PHL to SLC?
The 5am–8am departure window is the strongest at 84.4% on time. The 5pm–8pm window is the weakest at 70.6%, 14 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 December delays on PHL to SLC?
December is the weakest month at 52.5% on time, compared with 92.0% in April. Across the year that is 40 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
- SLC to PHL — the return legseparate record
- Philadelphia International (PHL) delay statistics
- Salt Lake City International (SLC) delay statistics
- Delta Air Lines on PHL to SLC78.3%
- American Airlines on PHL to SLC72.9%
- PHL to ATL, a related route79.2%
- DEN to SLC, a related route77.5%
- PHL to MCO, a related route72.4%
- Delta Air Lines on-time record78.3%
- American Airlines on-time record72.9%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. PHL to SLC and SLC to PHL 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.