Flight number record
UA 1233
United Airlines · Denver to Newark
- Route
- DEN → EWR
- Departs
- 11:37
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 1233, check with United Airlines.
UA 1233 lands a B, about a point better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 365 flights, with a median arrival 7 minutes early.
Key figures
On time
78.4%
Arrivals under 15 minutes late, of 352 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
1.64%
National rate is 1.89%
1 hour+ late
5.4%
National rate is 8.3%
These figures cover 365 flights between September 2025 and August 2026. The median arrival is 7 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 1233 flies
UA 1233 flies DEN to EWR without a single fixed slot. Its most common scheduled departure was 11:37, used on 66 of 365 flights, with 11:38 (60 flights) and 11:40 (40 flights) next.
- Departs 11:3766 flights18.1%
- Departs 11:3860 flights16.4%
- Departs 11:4040 flights11.0%
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 11:37 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.3%, and UA 1233 runs level with that at 78.4%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
UA 1233 next to DEN to EWR
Every carrier on DEN to EWR combined arrived on time 78.8% of the time across 3,344 flights, so UA 1233 is about level with it. Across its whole network United Airlines managed 78.8%, close to this flight's figure.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 1233 | 365 | 78.4% | 64 min | 1.64% | B |
| All United Airlines on DEN–EWR | 3,344 | 78.8% | 83 min | 1.53% | B |
| All carriers on DEN–EWR | 3,344 | 78.8% | 83 min | 1.53% | B |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 1233 quarter by quarter
UA 1233 did not run the same all year. Its best quarter was Apr–Jun 2026 at 82.4% on time and its weakest Jul–Sep 2025 at 70.0%, a swing of 12 points on roughly 73 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 flights70.0%
- Oct–Dec 202592 flights78.0%
- Jan–Mar 202690 flights80.2%
- Apr–Jun 202691 flights82.4%
- Jul–Sep 202662 flights74.1%
Scale runs 60% to 90%.
By weekday, UA 1233 did best on Tuesday at 89.8% on time and worst on Sunday at 66.7%. Each day rests on about 52 flights, so a gap of 23 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 1233 runs when it is late
UA 1233 often beats the schedule: 111 of 352 completed flights, 32%, arrived 15 minutes or more early. The 76 late arrivals split 34 under half an hour, 23 between 30 and 60 minutes, and 19 an hour or more.
- 15+ min early111 flights31.5%
- Within 15 min165 flights46.9%
- 15–29 min late34 flights9.7%
- 30–59 min late23 flights6.5%
- 1–2 hours late11 flights3.1%
- 2+ hours late8 flights2.3%
Scale runs 0% to 100%.
Share of 352 completed flights by arrival against schedule.
17 of 67 late departures made up the time and arrived on time, 25% of them. In the other direction, 26 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 EWR.
The worst days
Worst days for UA 1233
The latest arrival of the period was on 9 November 2025, 7 hours 49 minutes behind schedule; most of its delay minutes were filed as national airspace system delay. The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 9 November 2025 | 7 hours 49 minutes | National Airspace System |
| 20 August 2026 | 6 hours 46 minutes | National Airspace System |
| 11 August 2026 | 4 hours 45 minutes | National Airspace System |
| 19 December 2025 | 4 hours 20 minutes | Carrier |
| 6 July 2026 | 4 hours 11 minutes | Carrier |
Delay causes
Why UA 1233 runs late
National Airspace System accounts for 67% of the 4,843 delay minutes carriers reported here, and the remaining four split what is left.
- 67%National Airspace System
- 24%Carrier
- 9%Late-arriving aircraft
67% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 3,258 minutes out of 4,843, against a national NAS share of 21%. The split is drawn from 4,843 delay minutes reported on UA 1233.
Cancellations sit at 1.64% against a national 1.89%, which is ordinary. Diversions add another 1.92%.
Connections and routes
What a delay on this flight costs
5.4% of arrivals land an hour or more late, close to the national 8.3%, so 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.
At 1,605 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 nine other city pairs in the data, including SFO to DEN (71), EWR to FLL (56) and EWR to RDU (40), but none flew often enough under UA 1233 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to DEN to EWR only.
One caution: this is a thin sample. 365 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 1233
For a booking, read UA 1233 as 78.4% on time with 1.64% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- DEN to EWR, every carrier and departure
- EWR to DEN, the return direction
- United Airlines 1715 on the same route66.2%
- United Airlines 2613 on the same route70.1%
- United Airlines 1283 on the same route70.5%
- United Airlines 1505 on the same route69.0%
- United Airlines 2345 on the same route96.7%
- United Airlines 1745 on the same route91.6%
- Denver International (DEN) delay statistics
- Newark Liberty International (EWR) 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.