Route reliability record

PHX→SFO

Phoenix to San Francisco

Flights: 4,625
Period: June 2025 to May 2026
Distance: 651 mi
Carriers: 6

This route sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.4%. The late ones land about an hour behind schedule. That rests on 4,625 flights, of which United Airlines flew 1,454 at 76.3% on time.

United Airlines is the most reliable of the four carriers covered here at 76.3% on time across 1,454 flights.

On time

70.7%

Arrivals under 15 minutes late, of 4,595 completed flights

Avg delay

64 min

Across delayed arrivals only, not all flights

Cancelled

0.61%

National rate is 1.80%

Best carrier

United

76.3% on time across 1,454 flights

These figures cover 4,625 flights between June 2025 and May 2026. Beyond the headline rate, 10.3% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.

Carrier by carrier

Which airline is most reliable on PHX to SFO

The choice of carrier is not cosmetic here. United Airlines arrives on time 76.3% of the time; Southwest Airlines manages 62.6%. Sample sizes sit next to every figure, because a two-point gap across 1,079 flights means less than a ten-point one.

On-time performance by carrier on PHX to SFO
Airline	Flights	On time	Avg delay	Cancelled	Grade
Envoy Airthin sample	1	100.0%	—	0.00%	A+
United Airlines	1,454	76.3%	64 min	0.55%	B+
SkyWest Airlines	518	72.9%	67 min	0.19%	C+
Frontier Airlinesthin sample	254	71.2%	61 min	1.57%	C
American Airlines	1,319	70.1%	73 min	0.91%	C+
Southwest Airlines	1,079	62.6%	55 min	0.28%	D+

The spread between United 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 23 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am710 flights79.2%
8am–11am1,020 flights75.0%
11am–2pm545 flights69.5%
2pm–5pm791 flights75.0%
5pm–8pm980 flights65.4%
8pm–5am579 flights56.6%

Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 56.6% on time, against 79.2% 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.

Across the year

When delays peak on this route

This route's year swings by 38 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.

Darker means more delays. Figures are on-time percentages.March best, May worst

Delays peak in May, when the on-time rate falls to 45.1%. March is the strongest month at 83.2%. Moving a flexible trip across that boundary buys 38 points.

Across the week, Tuesday is the strongest day at 79.6% on time and Monday the weakest at 65.2%. 14 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 86,000 reported delay minutes.

National Airspace System
37%
Late-arriving aircraft
35%
Carrier
26%
Extreme weather
2%
Security
0%

35% 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 86,000 reported delay minutes here, that single category outweighs weather by 15 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.

37% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 32,000 minutes out of 86,000, against a national NAS share of 21%.

Cancellations are rare at 0.61%, 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

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.3% of arrivals land a full hour or more behind schedule, against 8.2% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

The 651 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 75.6% on time across 4,622 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.

The sample behind these figures is 4,625 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: the calendar is the biggest lever here, not the carrier or the hour. March runs 83.2% on time and May 45.1%, a swing of 38 points. If the dates move at all, move them out of May before you think about anything else.

Common questions

PHX to SFO questions

How often is PHX to SFO delayed?

Roughly one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 29.3% of the 4,625 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 SFO?

United Airlines leads at 76.3% on time across 1,454 flights. Southwest Airlines is at the other end on 62.6%, 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 SFO?

The 5am–8am departure window is the strongest at 79.2% on time. The 8pm–5am window is the weakest at 56.6%, 23 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 May delays on PHX to SFO?

May is the weakest month at 45.1% on time, compared with 83.2% in March. Across the year that is 38 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. PHX to SFO and SFO 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