Flight number record
UA 1339
United Airlines · Denver to San Juan
- Route
- DEN → SJU
- Departs
- 09:45
- Flights
- 326
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 1339, check with United Airlines.
UA 1339 earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 7 points better than the national rate of 77.3%. When something does go wrong the average delay runs roughly 45 minutes. That rests on 326 flights, with a median arrival 5 minutes early.
Set against the rest of the country, UA 1339's record is 7 points better than the US average of 77.3%. That gap is worth roughly 71 fewer late arrivals for every thousand flights.
Key figures
On time
84.4%
Arrivals under 15 minutes late, of 321 completed flights
Avg delay
47 min
Across delayed arrivals only, not all flights
Cancelled
0.31%
National rate is 1.89%
1 hour+ late
2.5%
National rate is 8.3%
These figures cover 326 flights between September 2025 and August 2026. The median arrival is 5 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.
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Schedule
When UA 1339 flies
UA 1339 flies DEN to SJU without a single fixed slot. Its most common scheduled departure was 09:45, used on 154 of 326 flights, with 09:43 (135 flights) and 09:50 (34 flights) next.
- Departs 09:45154 flights47.2%
- Departs 09:43135 flights41.4%
- Departs 09:5034 flights10.4%
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 09:45 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and UA 1339 runs level with that at 84.4%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
UA 1339 next to DEN to SJU
Across its whole network United Airlines managed 78.8%, which this flight beats by 6 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 1339thin sample | 326 | 84.4% | 47 min | 0.31% | B+ |
| All United Airlines on DEN–SJUthin sample | 326 | 84.4% | 47 min | 0.31% | B+ |
| All carriers on DEN–SJUthin sample | 326 | 84.4% | 47 min | 0.31% | B+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 1339 quarter by quarter
UA 1339 did not run the same all year. Its best quarter was Apr–Jun 2026 at 91.2% on time and its weakest Jul–Sep 2026 at 76.7%, a swing of 15 points on roughly 82 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 20259 flights—
- Oct–Dec 202592 flights86.8%
- Jan–Mar 202690 flights80.5%
- Apr–Jun 202691 flights91.2%
- Jul–Sep 202644 flights76.7%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
By weekday, UA 1339 did best on Wednesday at 95.5% on time and worst on Saturday at 68.6%. Each day rests on about 47 flights, so a gap of 27 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 1339 runs when it is late
The 50 late arrivals split 23 under half an hour, 19 between 30 and 60 minutes, and 8 an hour or more.
- 15+ min early79 flights24.6%
- Within 15 min192 flights59.8%
- 15–29 min late23 flights7.2%
- 30–59 min late19 flights5.9%
- 1–2 hours late6 flights1.9%
- 2+ hours late2 flights0.6%
Scale runs 0% to 100%.
Share of 321 completed flights by arrival against schedule.
6 of 32 late departures made up the time and arrived on time, 19% of them. In the other direction, 24 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 SJU.
The worst days
Worst days for UA 1339
The latest arrival of the period was on 25 July 2026, 5 hours 19 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across July, May, March, January and September, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 25 July 2026 | 5 hours 19 minutes | Carrier |
| 12 May 2026 | 3 hours 37 minutes | National Airspace System |
| 18 March 2026 | 1 hour 40 minutes | Carrier |
| 18 January 2026 | 1 hour 25 minutes | Late-arriving aircraft |
| 13 September 2025 | 1 hour 23 minutes | Late-arriving aircraft |
Delay causes
Why UA 1339 runs late
National Airspace System accounts for 49% of the 2,333 delay minutes carriers reported here, and the remaining four split what is left.
- 49%National Airspace System
- 42%Carrier
- 9%Late-arriving aircraft
The largest share of delay minutes, 42%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 969 of the 2,333 delay minutes reported here. The split is drawn from 2,333 delay minutes reported on UA 1339.
Cancellations are rare at 0.31%, 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
Badly late arrivals are rare here: only 2.5% land an hour or more behind schedule, against 8.3% 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 2,733 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 LAX to DEN (241), but none flew often enough under UA 1339 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to DEN to SJU 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 1339
For a booking, read UA 1339 as 84.4% on time with 0.31% cancelled over 326 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- Denver International (DEN) delay statistics
- Luis Munoz Marin International (SJU) 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.