Flight number record
UA 540
United Airlines · Denver to San Diego
- Route
- DEN → SAN
- Departs
- 19:00
- Flights
- 364
- Period
- July 2025 to June 2026
Historical statistics for July 2025 to June 2026, not live status. For today’s UA 540, check with United Airlines.
UA 540 draws a C+. About one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 364 flights, with a median arrival 2 minutes late.
The national on-time rate over the same period is 77.6%, so UA 540 runs 12 points behind the country as a whole. Across a thousand flights that is about 119 extra late arrivals.
Key figures
On time
65.7%
Arrivals under 15 minutes late, of 361 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
0.55%
National rate is 1.81%
1 hour+ late
10.8%
National rate is 8.1%
These figures cover 364 flights between July 2025 and June 2026. Beyond the headline rate, 10.8% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Schedule
When UA 540 flies
UA 540 flies DEN to SAN without a single fixed slot. Its most common scheduled departure was 19:00, used on 65 of 364 flights, with 19:14 (49 flights) and 19:20 (41 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.
- Departs 19:0065 flights17.9%
- Departs 19:1449 flights13.5%
- Departs 19:2041 flights11.3%
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 19:00 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and UA 540 runs 3 points worse at 65.7%. 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 540 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 540 is 10 points behind 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 trails by 13 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 540thin sample | 364 | 65.7% | 58 min | 0.55% | C+ |
| 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 540 quarter by quarter
UA 540 did not run the same all year. Its best quarter was Jan–Mar 2026 at 73.3% on time and its weakest Jul–Sep 2025 at 55.6%, a swing of 18 points on roughly 91 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 202592 flights55.6%
- Oct–Dec 202591 flights66.7%
- Jan–Mar 202690 flights73.3%
- Apr–Jun 202691 flights67.0%
Scale runs 45% to 80%. Rows with fewer than 30 flights show a dash.
By weekday, UA 540 did best on Tuesday at 71.2% on time and worst on Sunday at 51.9%. Each day rests on about 52 flights, so a gap of 19 points is worth noticing but could still narrow in another year.
Delay causes
Why UA 540 runs late
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 7,173 reported delay minutes.
- 36%Late-arriving aircraft
- 35%Carrier
- 29%National Airspace System
- 1%Extreme weather
36% 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 7,173 reported delay minutes here, that single category outweighs weather by 36 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 7,173 delay minutes reported on UA 540.
Cancellations are rare at 0.55%, 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.8% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
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 four other city pairs in the data, including SFO to DEN (41), BWI to DEN (36) and RDU to SFO (30), but none flew often enough under UA 540 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. 364 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 540
For a booking, UA 540 is one of the weaker ways to fly DEN to SAN: 10 points below the route as a whole. If the schedule allows, compare it with the other departures listed on the route page before settling on this one.
Related
Where to go next
- DEN to SAN, every carrier and departure
- SAN to DEN, the return direction
- United Airlines 1302 on the same route88.0%
- United Airlines 2309 on the same route90.3%
- 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
- 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.