Flight number record

UA 2423

United Airlines · Miami to San Francisco

Route: MIA → SFO
Departs: 18:35
Flights: 255
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 2423, check with United Airlines.

UA 2423 sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.6%. The late ones land an hour and a half behind schedule. That rests on 255 flights, with a median arrival right on schedule.

The national on-time rate over the same period is 77.6%, so UA 2423 runs 8 points behind the country as a whole. Across a thousand flights that is about 84 extra late arrivals.

On time

69.2%

Arrivals under 15 minutes late, of 253 completed flights

Avg delay

87 min

Across delayed arrivals only, not all flights

Cancelled

0.39%

National rate is 1.81%

1 hour+ late

13.8%

National rate is 8.1%

These figures cover 255 flights between July 2025 and June 2026. Beyond the headline rate, 13.8% 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 2423 flies

UA 2423 flies MIA to SFO without a single fixed slot. Its most common scheduled departure was 18:35, used on 117 of 255 flights, with 18:15 (55 flights) and 18:02 (45 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 18:35117 flights45.9%
Departs 18:1555 flights21.6%
Departs 18:0245 flights17.6%

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 18:35 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and UA 2423 runs level with that at 69.2%. 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 2423 next to MIA to SFO

Every carrier on MIA to SFO combined arrived on time 71.6% of the time across 1,725 flights, so UA 2423 is 2 points behind it. United flew 623 flights on the same city pair under all its flight numbers, including this one, and those ran 72.2% on time. Across its whole network United Airlines managed 79.0%, which this flight trails by 10 points.

UA 2423 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 2423thin sample	255	69.2%	87 min	0.39%	C+
All United Airlines on MIA–SFO	623	72.2%	71 min	0.32%	C+
All carriers on MIA–SFO	1,725	71.6%	65 min	0.70%	C+
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 2423 quarter by quarter

Quarter by quarter UA 2423 held fairly steady: 63.3% in Jul–Sep 2025, 72.4% in Oct–Dec 2025 and 72.4% in Jan–Mar 2026. A spread of 9 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202592 flights63.3%
Oct–Dec 202576 flights72.4%
Jan–Mar 202687 flights72.4%

Scale runs 55% to 80%. Rows with fewer than 30 flights show a dash.

By weekday, UA 2423 did best on Tuesday at 80.6% on time and worst on Sunday at 55.6%. Each day rests on about 36 flights, so a gap of 25 points is worth noticing but could still narrow in another year.

Delay causes

Why UA 2423 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 6,746 reported delay minutes.

Carrier
41%
National Airspace System
33%
Late-arriving aircraft
21%
Extreme weather
5%

The largest share of delay minutes, 41%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 2,747 of the 6,746 delay minutes reported here. The split is drawn from 6,746 delay minutes reported on UA 2423.

Cancellations are rare at 0.39%, 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. 13.8% 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.

At 2,585 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 three other city pairs in the data, including EWR to SNA (94), IAD to MIA (21) and LAS to SFO (16), but none flew often enough under UA 2423 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to MIA to SFO only.

One caution: this is a thin sample. 255 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 2423

For a booking, UA 2423 is a flight to put a long connection behind. 13.8% 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.

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