Flight number record
UA 737
United Airlines · Seattle to San Francisco
- Route
- SEA → SFO
- Departs
- 19:37
- Flights
- 362
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 737, check with United Airlines.
UA 737 earns an F+, which is as low as this site's scale goes for a reason. Only 53.9% of flights arrive inside the 15-minute window, 23 points worse than the national rate of 77.3%. Late arrivals average about an hour. Treat any tight connection here as a coin flip. That rests on 362 flights, with a median arrival 9 minutes late.
The national on-time rate over the same period is 77.3%, so UA 737 runs 23 points behind the country as a whole. Across a thousand flights that is about 234 extra late arrivals.
Key figures
On time
53.9%
Arrivals under 15 minutes late, of 360 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
0.55%
National rate is 1.89%
1 hour+ late
15.3%
National rate is 8.3%
These figures cover 362 flights between September 2025 and August 2026. Beyond the headline rate, 15.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When UA 737 flies
UA 737 flies SEA to SFO without a single fixed slot. Its most common scheduled departure was 19:37, used on 63 of 362 flights, with 13:30 (47 flights) and 17:20 (45 flights) next.
- Departs 19:3763 flights17.4%
- Departs 13:3047 flights13.0%
- Departs 17:2045 flights12.4%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 19:37 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and UA 737 runs 14 points worse at 53.9%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
UA 737 next to SEA to SFO
Every carrier on SEA to SFO combined arrived on time 59.8% of the time across 6,817 flights, so UA 737 is 6 points behind it. United flew 2,062 flights on the same city pair under all its flight numbers, including this one, and those ran 59.1% on time. Across its whole network United Airlines managed 78.8%, which this flight trails by 25 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 737thin sample | 362 | 53.9% | 63 min | 0.55% | F+ |
| All United Airlines on SEA–SFO | 2,062 | 59.1% | 67 min | 0.82% | D+ |
| All carriers on SEA–SFO | 6,817 | 59.8% | 57 min | 1.11% | D |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 737 quarter by quarter
UA 737 did not run the same all year. Its best quarter was Jan–Mar 2026 at 78.9% on time and its weakest Apr–Jun 2026 at 20.9%, a swing of 58 points on roughly 72 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
- Jul–Sep 202530 flights60.0%
- Oct–Dec 202589 flights71.3%
- Jan–Mar 202690 flights78.9%
- Apr–Jun 202691 flights20.9%
- Jul–Sep 202662 flights38.7%
Scale runs 10% to 85%.
By weekday, UA 737 did best on Tuesday at 70.6% on time and worst on Monday at 37.7%. Each day rests on about 52 flights, so a gap of 33 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 737 runs when it is late
The 166 late arrivals split 48 under half an hour, 63 between 30 and 60 minutes, and 55 an hour or more.
- 15+ min early87 flights24.2%
- Within 15 min107 flights29.7%
- 15–29 min late48 flights13.3%
- 30–59 min late63 flights17.5%
- 1–2 hours late36 flights10.0%
- 2+ hours late19 flights5.3%
Scale runs 0% to 100%.
Share of 360 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 133 departures that left 15 minutes late or more, only 11 made it up before arrival. In the other direction, 44 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SFO.
The worst days
Worst days for UA 737
The latest arrival of the period was on 5 January 2026, 4 hours 47 minutes behind schedule; most of its delay minutes were filed as national airspace system delay. The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 5 January 2026 | 4 hours 47 minutes | National Airspace System |
| 28 May 2026 | 4 hours 33 minutes | National Airspace System |
| 13 March 2026 | 4 hours 32 minutes | Late-arriving aircraft |
| 23 December 2025 | 4 hours 21 minutes | National Airspace System |
| 3 January 2026 | 4 hours 16 minutes | Extreme weather |
Delay causes
Why UA 737 runs late
National Airspace System accounts for 62% of the 10,000 delay minutes carriers reported here, and the remaining four split what is left.
- 62%National Airspace System
- 30%Late-arriving aircraft
- 5%Carrier
- 3%Extreme weather
62% 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 6,465 minutes out of 10,000, against a national NAS share of 21%. The split is drawn from 10,410 delay minutes reported on UA 737.
Cancellations are rare at 0.55%, below the national 1.89% 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 routes
What a delay on this flight costs
15.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
The 679 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.
The same number turns up on five other city pairs in the data, including SFO to ABQ (41), SFO to ORD (35) and SFO to EWR (24), but none flew often enough under UA 737 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SEA to SFO only.
One caution: this is a thin sample. 362 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.
What to do with this
Booking UA 737
For a booking, UA 737 is a flight to put a long connection behind. 15.3% of its completed flights arrived an hour or more late, which a short layover will not absorb. If the onward flight is on a separate ticket, the risk sits with you.
Related
Where to go next
- SEA to SFO, every carrier and departure
- SFO to SEA, the return direction
- Delta Air Lines 1412 on the same route60.1%
- Delta Air Lines 2635 on the same route69.6%
- SkyWest Airlines 3707 on the same route68.5%
- Alaska Airlines 655 on the same route67.2%
- Alaska Airlines 725 on the same route50.5%
- SkyWest Airlines 3991 on the same route59.9%
- Seattle-Tacoma International (SEA) delay statistics
- San Francisco International (SFO) delay statistics
- United Airlines on-time record
- Every United Airlines flight number with a record
- The most and least reliable flight numbers in the US
- The best time of day to fly, according to 7.05 million flight records
A flight number here means United Airlines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
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.