Route reliability record

PHX→SLC

Phoenix to Salt Lake City

Flights: 5,749
Period: June 2025 to May 2026
Distance: 507 mi
Carriers: 6

This route lands a B+, 6 points better than the national rate of 77.4%. About one flight in six arrive 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 5,749 flights, of which Delta Air Lines flew 1,709 at 90.2% on time.

Delta Air Lines is the most reliable of the four carriers covered here at 90.2% on time across 1,709 flights.

On time

83.2%

Arrivals under 15 minutes late, of 5,707 completed flights

Avg delay

61 min

Across delayed arrivals only, not all flights

Cancelled

0.63%

National rate is 1.80%

Best carrier

Delta

90.2% on time across 1,709 flights

These figures cover 5,749 flights between June 2025 and May 2026. The median arrival is 8 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 SLC

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 90.2% of the time; Southwest Airlines manages 76.2%. Sample sizes sit next to every figure, because a two-point gap across 1,857 flights means less than a ten-point one.

On-time performance by carrier on PHX to SLC
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,709	90.2%	77 min	0.59%	A+
American Airlinesthin sample	296	87.4%	73 min	0.34%	A+
SkyWest Airlines	1,115	83.4%	63 min	0.27%	B+
Frontier Airlines	657	82.7%	80 min	2.13%	B
Envoy Airthin sample	115	82.6%	47 min	0.00%	B+
Southwest Airlines	1,857	76.2%	48 min	0.43%	B+

The spread between Delta and Southwest is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 more arrivals inside the on-time window.

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 27 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am682 flights95.4%
8am–11am1,296 flights88.1%
11am–2pm830 flights85.5%
2pm–5pm1,051 flights81.4%
5pm–8pm1,266 flights78.6%
8pm–5am624 flights68.9%

Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 95.4% of the time, against 68.9% for the overnight window. That is 27 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.

Across the year

When delays peak on this route

Twelve months, one bar each, drawn from the same 5,749 flights. The strip shows how much of this route's record is set by the calendar rather than by the operation.

Darker means more delays. Figures are on-time percentages.September best, April worst

September is the best month on the calendar at 86.6% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back.

Across the week, Tuesday is the strongest day at 88.3% on time and Sunday the weakest at 79.8%. 9 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. Late-arriving aircraft accounts for 53% of the 58,000 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.

Late-arriving aircraft
53%
Carrier
40%
National Airspace System
6%
Extreme weather
1%
Security
0%

53% 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 58,000 reported delay minutes here, that single category outweighs weather by 38 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 largest share of delay minutes, 40%, 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 23,000 of the 58,000 delay minutes reported here.

Cancellations are rare at 0.63%, below the national 1.80% 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

5.1% of arrivals land an hour or more late, close to the national 8.2%. 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 are the about an hour kind, which a normal layover absorbs.

The 507 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 runs 84.1% on time across 5,752 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 5,749 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.

What to do with this

Booking this route

Put together: avoid the 8pm–5am departure. It runs 68.9% on time against 95.4% for the 5am–8am slot, and that 27 points is the largest single thing you control here. Delta Air Lines is the strongest operator if the fares are close.

Common questions

PHX to SLC questions

How often is PHX to SLC delayed?

About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 16.8% of the 5,749 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on PHX to SLC?

Delta Air Lines leads at 90.2% on time across 1,709 flights. Southwest Airlines is at the other end on 76.2%, a gap of 14 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 SLC?

The 5am–8am departure window is the strongest at 95.4% on time. The 8pm–5am window is the weakest at 68.9%, 27 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 April delays on PHX to SLC?

April is the weakest month at 79.7% on time, compared with 86.6% in September. Across the year that is 7 points between the best and worst months. The seasonal swing is modest enough that it should not decide when you travel.

Where to go next

Direction matters. PHX to SLC and SLC to PHX are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.

Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.

Key figures