Carrier route record

UAORD→SJU

United Airlines · Chicago to San Juan

Flights: 657
Period: September 2025 to August 2026
Share of route: 47%
Carriers: 4

Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.

United on ORD to SJU lands a B+, 2 points 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 roughly 50 minutes on average. That rests on 657 flights, with a median arrival 4 minutes early.

The US average over the same twelve months is 77.3%, so there is little to separate United on ORD to SJU from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

79.2%

Arrivals under 15 minutes late, of 655 completed flights

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

0.30%

National rate is 1.89%

Whole route

73.2%

Every carrier on ORD to SJU, 1,390 flights

These figures cover 657 flights between September 2025 and August 2026. The median arrival is 4 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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Carrier by carrier

United against every carrier on ORD to SJU

United flew 657 of the 1,390 flights on ORD to SJU, about 47% of it. Its 79.2% on time is 6 points better than the route as a whole, which runs 73.2%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from United at 79.2% to Spirit at 60.8%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on ORD to SJU
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines (this page)	657	79.2%	52 min	0.30%	B+
American Airlines	429	71.2%	64 min	1.63%	C
Frontier Airlinesthin sample	72	66.7%	189 min	4.17%	C−
Spirit Airlinesthin sample	232	60.8%	76 min	8.19%	D−

Flight by flight

United flight numbers on ORD to SJU

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Departure window

When United runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 657 flights.

5am–8am4 flights—
8am–11am365 flights79.1%
11am–2pm—
2pm–5pm288 flights79.4%
5pm–8pm—
8pm–5am—

Scale runs 70% to 85%. Rows with fewer than 30 flights show a dash.

The 2pm–5pm window is the strongest at 79.4% on time. The full set of windows spans half a point.

Across the year

United on ORD to SJU through the year

Darker means more delays. Figures are on-time percentages.February best, March worst

Delays peak in March, when the on-time rate falls to 62.1%. February is the strongest month at 98.2%. Moving a flexible trip across that boundary buys 36 points. March was the busiest month here, with 66 flights.

Across the week, Wednesday is the strongest day at 84.9% on time and Monday the weakest at 70.5%, a spread of 14 points.

Arrival by arrival

How late United on ORD to SJU runs when it is late

United on ORD to SJU often beats the schedule: 171 of 655 completed flights, 26%, arrived 15 minutes or more early. The 136 late arrivals split 54 under half an hour, 50 between 30 and 60 minutes, and 32 an hour or more.

15+ min early171 flights26.1%
Within 15 min348 flights53.1%
15–29 min late54 flights8.2%
30–59 min late50 flights7.6%
1–2 hours late17 flights2.6%
2+ hours late15 flights2.3%

Scale runs 0% to 100%.

Share of 655 completed flights by arrival against schedule.

20 of 100 late departures made up the time and arrived on time, 20% of them. In the other direction, 56 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 United on ORD to SJU

The latest arrival of the period was on 12 August 2026, 6 hours 15 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across August, July, March and November, with no single month standing out.

The latest arrivals of United on ORD to SJU in the period
Date	Arrived late by	Largest filed cause
12 August 2026	6 hours 15 minutes	Carrier
27 July 2026	3 hours 37 minutes	Late-arriving aircraft
15 August 2026	3 hours 28 minutes	Carrier
16 March 2026	2 hours 49 minutes	Extreme weather
8 November 2025	2 hours 37 minutes	Late-arriving aircraft

Delay causes

Why United runs late on this route

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 7,069 reported delay minutes.

National Airspace System
35%
Carrier
35%
Late-arriving aircraft
24%
Extreme weather
6%

The largest share of delay minutes, 35%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,474 of the 7,069 delay minutes reported here. The split is drawn from 7,069 reported delay minutes.

35% 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 2,476 minutes out of 7,069, against a national NAS share of 21%.

Cancellations are rare at 0.30%, 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 stage length

What a delay here costs

Badly late arrivals are rare here: only 4.9% 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 2,072 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 return leg runs 80.5% on time across 657 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 657 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 United on ORD to SJU

Put together: treat all of this as provisional. 657 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 79.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 655 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures