Route reliability record
PHL→SLC
Philadelphia to Salt Lake City
- Flights
- 804
- Period
- September 2025 to August 2026
- Distance
- 1,927 mi
- Carriers
- 2
This route lands a B, about a point 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 804 PHL to SLC flights, with a median arrival 3 minutes early.
Best time to fly PHL to SLC: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 84.4% of the time and Tuesday flights 84.2%, against 78.4% 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
78.4%
Arrivals under 15 minutes late, of 787 completed flights
Avg delay
86 min
Across delayed arrivals only, not all flights
Cancelled
1.99%
National rate is 1.89%
Best carrier
Delta
79.6% on time across 591 flights
These figures cover 804 flights between September 2025 and August 2026. The median arrival is 3 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.
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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 | 591 | 79.6% | 66 min | 1.18% | B |
| American Airlinesthin sample | 213 | 74.9% | 132 min | 4.23% | 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.
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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 19 points, against half a point between the best and worst carrier.
- 5am–8am365 flights84.4%
- 8am–11am—
- 11am–2pm—
- 2pm–5pm3 flights—
- 5pm–8pm393 flights74.2%
- 8pm–5am43 flights65.0%
Scale runs 55% 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 65.0% for the overnight window. That is 19 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 393 flights scheduled in it.
Explore
Filter PHL to SLC 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 PHL to SLC, the best departure window is 5am–8am at 84.4% on time and the worst is 8pm–5am at 65.0%, a wide gap of 19.4 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am84.4%
- 8–11am—
- 11am–2pm—
- 2–5pm—
- 5–8pm74.2%
- 8pm–5am65.0%
best all US flightsScale 55% to 95%. Cells under 30 flights show a dash.
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. March was the busiest month here, with 89 flights.
Across the week, Tuesday is the strongest day at 84.2% on time and Thursday the weakest at 68.0%, a spread of 16 points.
Delay causes
Why this route gets delayed
Carrier accounts for 49% of the 15,000 delay minutes carriers reported here, and the remaining four split what is left.
- 49%Carrier
- 22%National Airspace System
- 20%Late-arriving aircraft
- 9%Extreme weather
The largest share of delay minutes, 49%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 7,172 of the 15,000 delay minutes reported here. The split is drawn from 14,577 reported delay minutes.
Cancellations sit at 1.99% against a national 1.89%, which is ordinary. Diversions add another 0.12%.
Connections and stage length
What a delay here actually costs
7.5% 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 an hour and a half, 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 83.8% on time across 805 flights, 5 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 5 points of difference.
One caution: this is a thin sample. 804 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. 804 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 78.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 787 completed flights over 12 months sit behind that.
Common questions
PHL to SLC questions
How often is PHL to SLC 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 21.6% of the 804 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
How reliable is PHL to SLC compared with the rest of the country?
78.4% of flights arrive on time here against a national 77.3%, a difference of about a point in its favour. 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 8pm–5am window is the weakest at 65.0%, 19 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 SLC79.6%
- American Airlines on PHL to SLC74.9%
- PHL to ATL, a related route78.0%
- DEN to SLC, a related route78.2%
- PHL to MCO, a related route72.4%
- Delta Air Lines on-time record79.6%
- American Airlines on-time record74.9%
- The best time of day to fly, according to 7.05 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.