Flight number record

UA 1233

United Airlines · Denver to Newark

Route: DEN → EWR
Departs: 11:37
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 1233, check with United Airlines.

UA 1233 lands a B, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 365 flights, with a median arrival 6 minutes early.

On time

76.2%

Arrivals under 15 minutes late, of 357 completed flights

Avg delay

63 min

Across delayed arrivals only, not all flights

Cancelled

1.64%

National rate is 1.81%

1 hour+ late

6.2%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 2026. The median arrival is 6 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 1233 flies

UA 1233 flies DEN to EWR without a single fixed slot. Its most common scheduled departure was 11:37, used on 64 of 365 flights, with 11:38 (60 flights) and 11:40 (49 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 11:3764 flights17.5%
Departs 11:3860 flights16.4%
Departs 11:4049 flights13.4%

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 11:37 departure sits in the 11am–2pm window. Across every US flight scheduled in that window the on-time rate is 78.8%, and UA 1233 runs 3 points worse at 76.2%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

UA 1233 next to DEN to EWR

Every carrier on DEN to EWR combined arrived on time 77.5% of the time across 3,363 flights, so UA 1233 is about level with it. Across its whole network United Airlines managed 79.0%, which this flight trails by 3 points.

UA 1233 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 1233	365	76.2%	63 min	1.64%	B
All United Airlines on DEN–EWR	3,363	77.5%	80 min	1.58%	B
All carriers on DEN–EWR	3,363	77.5%	80 min	1.58%	B
United Airlines, whole network	821,041	79.0%	72 min	1.01%	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 64.0%, 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 flights64.0%
Oct–Dec 202592 flights78.0%
Jan–Mar 202690 flights80.2%
Apr–Jun 202691 flights82.4%

Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.

By weekday, UA 1233 did best on Tuesday at 88.5% on time and worst on Sunday at 64.7%. Each day rests on about 52 flights, so a gap of 24 points is worth noticing but could still narrow in another year.

Delay causes

Why UA 1233 runs late

One category carries most of the weight here. National Airspace System accounts for 60% of the 5,323 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.

National Airspace System
60%
Late-arriving aircraft
23%
Carrier
15%
Extreme weather
3%

60% 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 3,191 minutes out of 5,323, against a national NAS share of 21%. The split is drawn from 5,323 delay minutes reported on UA 1233.

Cancellations sit at 1.64% against a national 1.81%, which is ordinary. Diversions add another 0.55%.

Connections and routes

What a delay on this flight costs

6.2% 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.

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 ten other city pairs in the data, including SFO to DEN (71), EWR to FLL (56) and SJC to DEN (49), 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 76.2% on time with 1.64% cancelled over 365 flights. Those are rates from the past twelve months, not a forecast for any particular day.

Where to go next

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.

Key figures