Flight number record

UA 2129

United Airlines · San Diego to Washington

Route: SAN → IAD
Departs: 21:45
Flights: 326
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 2129, check with United Airlines.

UA 2129 earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 13 points better than the national rate of 77.6%. When something does go wrong the average delay runs about 2.5 hours. That rests on 326 flights, with a median arrival 14 minutes early.

Set against the rest of the country, UA 2129's record is 13 points better than the US average of 77.6%. That gap is worth roughly 125 fewer late arrivals for every thousand flights.

On time

90.1%

Arrivals under 15 minutes late, of 323 completed flights

Avg delay

151 min

Across delayed arrivals only, not all flights

Cancelled

0.92%

National rate is 1.81%

1 hour+ late

2.8%

National rate is 8.1%

These figures cover 326 flights between July 2025 and June 2026. The median arrival is 14 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.

Schedule

When UA 2129 flies

UA 2129 flies SAN to IAD without a single fixed slot. Its most common scheduled departure was 21:45, used on 108 of 326 flights, with 22:00 (87 flights) and 22:15 (58 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 21:45108 flights33.1%
Departs 22:0087 flights26.7%
Departs 22:1558 flights17.8%

Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.

Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.

A 21:45 departure sits in the 8pm–5am window. Across every US flight scheduled in that window the on-time rate is 70.5%, and UA 2129 runs 20 points better at 90.1%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.

Against the route

UA 2129 next to SAN to IAD

Every carrier on SAN to IAD combined arrived on time 89.0% of the time across 1,400 flights, so UA 2129 is about level with it. United flew 1,040 flights on the same city pair under all its flight numbers, including this one, and those ran 89.5% on time. Across its whole network United Airlines managed 79.0%, which this flight beats by 11 points.

UA 2129 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 2129thin sample	326	90.1%	151 min	0.92%	A+
All United Airlines on SAN–IAD	1,040	89.5%	87 min	0.48%	A+
All carriers on SAN–IAD	1,400	89.0%	78 min	0.57%	A+
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 2129 quarter by quarter

Quarter by quarter UA 2129 held fairly steady: 88.9% in Jul–Sep 2025, 90.7% in Oct–Dec 2025, 86.8% in Jan–Mar 2026 and 93.7% in Apr–Jun 2026. A spread of 7 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202591 flights88.9%
Oct–Dec 202586 flights90.7%
Jan–Mar 202670 flights86.8%
Apr–Jun 202679 flights93.7%

Scale runs 80% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, UA 2129 ranged from 86.5% on Friday to 95.6% on Tuesday. With about 47 flights behind each day, a spread of 9 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why UA 2129 runs late

One category carries most of the weight here. Carrier accounts for 54% of the 4,834 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.

Carrier
54%
Extreme weather
28%
Late-arriving aircraft
13%
National Airspace System
6%

Extreme weather accounts for 28% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 4.5 times the usual weather exposure. The split is drawn from 4,834 delay minutes reported on UA 2129.

Cancellations sit at 0.92% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and routes

What a delay on this flight costs

Badly late arrivals are rare here: only 2.8% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

At 2,253 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 same number turns up on one other city pair in the data, including SFO to LAS (5), but none flew often enough under UA 2129 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SAN to IAD only.

One caution: this is a thin sample. 326 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 2129

For a booking, UA 2129 has one of the better records a US domestic flight can show: 90.1% on time and 0.92% cancelled. That is a base rate, not a promise about any single day.

Where to go next

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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures