Flight number record
UA 519
United Airlines · San Diego to Denver
- Route
- SAN → DEN
- Departs
- 18:55
- Flights
- 272
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 2026, not live status. For today’s UA 519, check with United Airlines.
UA 519 earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs about an hour. That rests on 272 flights, with a median arrival 18 minutes early.
Set against the rest of the country, UA 519's record is 8 points better than the US average of 77.6%. That gap is worth roughly 75 fewer late arrivals for every thousand flights.
Key figures
On time
85.1%
Arrivals under 15 minutes late, of 268 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
1.47%
National rate is 1.81%
1 hour+ late
5.2%
National rate is 8.1%
These figures cover 272 flights between July 2025 and June 2026. The median arrival is 18 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 519 flies
UA 519 flies SAN to DEN without a single fixed slot. Its most common scheduled departure was 18:55, used on 97 of 272 flights, with 18:47 (68 flights) and 19:14 (28 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 18:5597 flights35.7%
- Departs 18:4768 flights25.0%
- Departs 19:1428 flights10.3%
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 18:55 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and UA 519 runs 17 points better at 85.1%. 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 519 next to SAN to DEN
Every carrier on SAN to DEN combined arrived on time 79.2% of the time across 5,947 flights, so UA 519 is 6 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 85.4% on time. Across its whole network United Airlines managed 79.0%, which this flight beats by 6 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 519thin sample | 272 | 85.1% | 56 min | 1.47% | A |
| All United Airlines on SAN–DEN | 2,081 | 85.4% | 65 min | 0.77% | A+ |
| All carriers on SAN–DEN | 5,947 | 79.2% | 60 min | 0.89% | B+ |
| United Airlines, whole network | 821,041 | 79.0% | 72 min | 1.01% | B |
Across the year
UA 519 quarter by quarter
UA 519 did not run the same all year. Its best quarter was Jan–Mar 2026 at 92.6% on time and its weakest Jul–Sep 2025 at 68.9%, a swing of 24 points on roughly 68 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 202576 flights68.9%
- Oct–Dec 202568 flights91.2%
- Jan–Mar 202656 flights92.6%
- Apr–Jun 202672 flights90.3%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
By weekday, UA 519 ranged from 79.6% on Thursday to 89.8% on Sunday. With about 39 flights behind each day, a spread of 10 points is inside normal variation, so the day you fly is not worth changing for this flight.
Delay causes
Why UA 519 runs late
One category carries most of the weight here. Late-arriving aircraft accounts for 76% of the 2,241 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.
- 76%Late-arriving aircraft
- 18%National Airspace System
- 6%Carrier
76% 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 2,241 reported delay minutes here, that single category outweighs weather by 76 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 2,241 delay minutes reported on UA 519.
Cancellations sit at 1.47% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
5.2% 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 last about an hour, which a normal layover absorbs.
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 eight other city pairs in the data, including DEN to MCO (128), DEN to SNA (7) and ORD to MSY (6), but none flew often enough under UA 519 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SAN to DEN only.
One caution: this is a thin sample. 272 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 519
For a booking, UA 519 has one of the better records a US domestic flight can show: 85.1% on time and 1.47% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- SAN to DEN, every carrier and departure
- DEN to SAN, the return direction
- United Airlines 682 on the same route73.5%
- Frontier Airlines 2818 on the same route84.4%
- United Airlines 2476 on the same route89.5%
- United Airlines 1337 on the same route88.5%
- San Diego International (SAN) delay statistics
- Denver International (DEN) 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
- Why the first flight of the morning is statistically safest
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.