Flight number record
UA 540
United Airlines · Denver to San Diego
- Route
- DEN → SAN
- Departs
- 19:20
- Flights
- 364
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 540, check with United Airlines.
UA 540 draws a D+. Roughly 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 4 minutes late.
The national on-time rate over the same period is 77.3%, so UA 540 runs 14 points behind the country as a whole. Across a thousand flights that is about 138 extra late arrivals.
Key figures
On time
63.5%
Arrivals under 15 minutes late, of 362 completed flights
Avg delay
62 min
Across delayed arrivals only, not all flights
Cancelled
0.27%
National rate is 1.89%
1 hour+ late
12.4%
National rate is 8.3%
These figures cover 364 flights between September 2025 and August 2026. Beyond the headline rate, 12.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
Fare search by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Schedule
When UA 540 flies
UA 540 flies DEN to SAN without a single fixed slot. Its most common scheduled departure was 19:20, used on 82 of 364 flights, with 19:00 (52 flights) and 19:10 (37 flights) next.
- Departs 19:2082 flights22.5%
- Departs 19:0052 flights14.3%
- Departs 19:1037 flights10.2%
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 19:20 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and UA 540 runs 5 points worse at 63.5%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Against the route
UA 540 next to DEN to SAN
Every carrier on DEN to SAN combined arrived on time 73.8% of the time across 6,152 flights, so UA 540 is 10 points behind it. United flew 2,067 flights on the same city pair under all its flight numbers, including this one, and those ran 77.9% on time. Across its whole network United Airlines managed 78.8%, which this flight trails by 15 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 540thin sample | 364 | 63.5% | 62 min | 0.27% | D+ |
| All United Airlines on DEN–SAN | 2,067 | 77.9% | 59 min | 0.34% | B+ |
| All carriers on DEN–SAN | 6,152 | 73.8% | 56 min | 0.83% | C+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | 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 2026 at 37.1%, a swing of 36 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 202530 flights—
- Oct–Dec 202591 flights66.7%
- Jan–Mar 202690 flights73.3%
- Apr–Jun 202691 flights67.0%
- Jul–Sep 202662 flights37.1%
Scale runs 30% to 80%. Rows with fewer than 30 flights show a dash.
By weekday, UA 540 did best on Tuesday at 72.5% on time and worst on Sunday at 46.2%. Each day rests on about 52 flights, so a gap of 26 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 540 runs when it is late
The 132 late arrivals split 39 under half an hour, 48 between 30 and 60 minutes, and 45 an hour or more.
- 15+ min early47 flights13.0%
- Within 15 min183 flights50.6%
- 15–29 min late39 flights10.8%
- 30–59 min late48 flights13.3%
- 1–2 hours late30 flights8.3%
- 2+ hours late15 flights4.1%
Scale runs 0% to 100%.
Share of 362 completed flights by arrival against schedule.
20 of 129 late departures made up the time and arrived on time, 16% of them. In the other direction, 23 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 SAN.
The worst days
Worst days for UA 540
The latest arrival of the period was on 21 August 2026, 4 hours 51 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. Three of the five worst days fell in August 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 21 August 2026 | 4 hours 51 minutes | Late-arriving aircraft |
| 19 December 2025 | 4 hours 46 minutes | Late-arriving aircraft |
| 14 August 2026 | 4 hours 37 minutes | Late-arriving aircraft |
| 23 August 2026 | 4 hours 26 minutes | Late-arriving aircraft |
| 2 January 2026 | 4 hours 8 minutes | National Airspace System |
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 8,158 reported delay minutes.
- 37%Late-arriving aircraft
- 33%National Airspace System
- 30%Carrier
- 0%Extreme weather
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 8,158 reported delay minutes here, that single category outweighs weather by 37 to one. The split is drawn from 8,158 delay minutes reported on UA 540.
Cancellations are rare at 0.27%, 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
12.4% 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 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.
The same number turns up on four other city pairs in the data, including SFO to DEN (103), 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 a flight to put a long connection behind. 12.4% 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
- DEN to SAN, every carrier and departure
- SAN to DEN, the return direction
- United Airlines 1940 on the same route78.4%
- United Airlines 1302 on the same route83.6%
- United Airlines 2309 on the same route90.9%
- United Airlines 1281 on the same route83.3%
- Frontier Airlines 4989 on the same route73.6%
- 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.