Flight number record
UA 2309
United Airlines · Denver to San Diego
- Route
- DEN → SAN
- Departs
- 07:45
- Flights
- 343
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 2026, not live status. For today’s UA 2309, check with United Airlines.
UA 2309 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 roughly 50 minutes. That rests on 343 flights, with a median arrival 13 minutes early.
Set against the rest of the country, UA 2309's record is 13 points better than the US average of 77.6%. That gap is worth roughly 127 fewer late arrivals for every thousand flights.
Key figures
On time
90.3%
Arrivals under 15 minutes late, of 341 completed flights
Avg delay
48 min
Across delayed arrivals only, not all flights
Cancelled
0.29%
National rate is 1.81%
1 hour+ late
2.3%
National rate is 8.1%
These figures cover 343 flights between July 2025 and June 2026. The median arrival is 13 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 2309 flies
UA 2309 flies DEN to SAN without a single fixed slot. Its most common scheduled departure was 07:45, used on 251 of 343 flights. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 07:45251 flights73.2%
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 07:45 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and UA 2309 runs level with that at 90.3%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
Against the route
UA 2309 next to DEN to SAN
Every carrier on DEN to SAN combined arrived on time 75.6% of the time across 5,949 flights, so UA 2309 is 15 points ahead of it. United flew 2,081 flights on the same city pair under all its flight numbers, including this one, and those ran 79.8% on time. Across its whole network United Airlines managed 79.0%, which this flight beats by 11 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 2309thin sample | 343 | 90.3% | 48 min | 0.29% | A+ |
| All United Airlines on DEN–SAN | 2,081 | 79.8% | 59 min | 0.48% | B+ |
| All carriers on DEN–SAN | 5,949 | 75.6% | 56 min | 0.66% | B+ |
| United Airlines, whole network | 821,041 | 79.0% | 72 min | 1.01% | B |
Across the year
UA 2309 quarter by quarter
Quarter by quarter UA 2309 held fairly steady: 84.8% in Jul–Sep 2025, 91.1% in Oct–Dec 2025, 92.6% in Jan–Mar 2026 and 93.4% in Apr–Jun 2026. A spread of 9 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202592 flights84.8%
- Oct–Dec 202591 flights91.1%
- Jan–Mar 202669 flights92.6%
- Apr–Jun 202691 flights93.4%
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
By weekday, UA 2309 ranged from 85.4% on Friday to 96.0% on Tuesday. With about 49 flights behind each day, a spread of 11 points is inside normal variation, so the day you fly is not worth changing for this flight.
Delay causes
Why UA 2309 runs late
One category carries most of the weight here. National Airspace System accounts for 43% of the 1,579 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.
- 43%National Airspace System
- 36%Carrier
- 21%Late-arriving aircraft
The largest share of delay minutes, 36%, 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 568 of the 1,579 delay minutes reported here. The split is drawn from 1,579 delay minutes reported on UA 2309.
Cancellations are rare at 0.29%, 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 routes
What a delay on this flight costs
Badly late arrivals are rare here: only 2.3% 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.
The 853 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 same number turns up on two other city pairs in the data, including SAN to SFO (143) and MCI to DEN (3), but none flew often enough under UA 2309 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to DEN to SAN only.
One caution: this is a thin sample. 343 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 2309
For a booking, UA 2309 has one of the better records a US domestic flight can show: 90.3% on time and 0.29% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- DEN to SAN, every carrier and departure
- SAN to DEN, the return direction
- United Airlines 540 on the same route65.7%
- United Airlines 1302 on the same route88.0%
- United Airlines 1940 on the same route82.0%
- United Airlines 1281 on the same route84.6%
- United Airlines 1835 on the same route65.7%
- Denver International (DEN) delay statistics
- San Diego International (SAN) 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
- Worst months to fly in the US, ranked by the data
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.