Route reliability record

SFO→PDX

San Francisco to Portland

Flights: 3,514
Period: July 2025 to June 2026
Distance: 550 mi
Carriers: 4

This route lands a B+, 3 points better than the national rate of 77.6%. About one flight in five 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 3,514 flights, of which United Airlines flew 1,661 at 81.1% on time.

United Airlines is the most reliable of the three carriers covered here at 81.1% on time across 1,661 flights.

On time

80.4%

Arrivals under 15 minutes late, of 3,502 completed flights

Avg delay

59 min

Across delayed arrivals only, not all flights

Cancelled

0.34%

National rate is 1.81%

Best carrier

United

81.1% on time across 1,661 flights

These figures cover 3,514 flights between July 2025 and June 2026. The median arrival is 6 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 SFO to PDX

The three carriers here are closely matched: 3 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on SFO to PDX
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	1,661	81.1%	63 min	0.18%	B+
Alaska Airlines	1,383	80.2%	57 min	0.51%	B+
SkyWest Airlines	457	78.3%	56 min	0.22%	B+
Frontier Airlinesthin sample	13	75.0%	62 min	7.69%	B−

No carrier stands out. United tops the table at 81.1%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.

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

5am–8am194 flights93.8%
8am–11am638 flights86.3%
11am–2pm732 flights76.8%
2pm–5pm661 flights75.2%
5pm–8pm677 flights80.9%
8pm–5am612 flights79.2%

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 93.8% of the time, against 75.2% for the afternoon 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 11am–2pm window is the busiest, with 732 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 21 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 67.9%. March is the strongest month at 89.2%. Moving a flexible trip across that boundary buys 21 points. October was the busiest month here, with 344 flights.

Across the week, Saturday is the strongest day at 86.6% on time and Thursday the weakest at 75.1%. 12 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 58% of the 41,000 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
58%
Carrier
31%
National Airspace System
11%
Extreme weather
0%
Security
0%

58% 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 41,000 reported delay minutes here, that single category outweighs weather by 58 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 40,822 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 93.8% on time here.

Cancellations are rare at 0.34%, 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

6.0% 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 are the about an hour kind, which a normal layover absorbs.

The 550 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 72.3% on time across 3,516 flights, 8 points below 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.

The sample behind these figures is 3,514 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 89.2% on time and May 67.9%, a swing of 21 points. If the dates move at all, move them out of May before you think about anything else. 3,502 completed flights over 12 months sit behind that.

Common questions

SFO to PDX questions

How often is SFO to PDX delayed?

About one flight in five arrive 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 3,514 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on SFO to PDX?

United Airlines leads at 81.1% on time across 1,661 flights. SkyWest Airlines is at the other end on 78.3%, a gap of 3 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 SFO to PDX?

The 5am–8am departure window is the strongest at 93.8% on time. The 2pm–5pm window is the weakest at 75.2%, 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 May delays on SFO to PDX?

May is the weakest month at 67.9% on time, compared with 89.2% in March. Across the year that is 21 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. SFO to PDX and PDX to SFO 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, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures