Flight number record
UA 668
United Airlines · San Juan to Houston
- Route
- SJU → IAH
- Departs
- 14:55
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 668, check with United Airlines.
UA 668 lands a B+, 3 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 365 flights, with a median arrival 6 minutes early.
Key figures
On time
80.7%
Arrivals under 15 minutes late, of 363 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
0.27%
National rate is 1.89%
1 hour+ late
4.1%
National rate is 8.3%
These figures cover 365 flights between September 2025 and August 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.
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Schedule
When UA 668 flies
UA 668 flies SJU to IAH without a single fixed slot. Its most common scheduled departure was 14:55, used on 189 of 365 flights, with 15:46 (126 flights) next.
- Departs 14:55189 flights51.8%
- Departs 15:46126 flights34.5%
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 14:55 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 71.9%, and UA 668 runs 9 points better at 80.7%. 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 668 next to SJU to IAH
Every carrier on SJU to IAH combined arrived on time 88.7% of the time across 909 flights, so UA 668 is 8 points behind it. United flew 864 flights on the same city pair under all its flight numbers, including this one, and those ran 89.5% on time. Across its whole network United Airlines managed 78.8%, which this flight beats by 2 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 668 | 365 | 80.7% | 52 min | 0.27% | B+ |
| All United Airlines on SJU–IAH | 864 | 89.5% | 52 min | 0.46% | A+ |
| All carriers on SJU–IAH | 909 | 88.7% | 55 min | 0.55% | A+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 668 quarter by quarter
UA 668 did not run the same all year. Its best quarter was Jul–Sep 2025 at 90.0% on time and its weakest Oct–Dec 2025 at 72.8%, a swing of 17 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 flights90.0%
- Oct–Dec 202592 flights72.8%
- Jan–Mar 202690 flights80.7%
- Apr–Jun 202691 flights81.3%
- Jul–Sep 202662 flights87.1%
Scale runs 65% to 95%.
By weekday, UA 668 did best on Tuesday at 86.5% on time and worst on Sunday at 73.1%. Each day rests on about 52 flights, so a gap of 13 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 668 runs when it is late
UA 668 often beats the schedule: 121 of 363 completed flights, 33%, arrived 15 minutes or more early. The 70 late arrivals split 26 under half an hour, 29 between 30 and 60 minutes, and 15 an hour or more.
- 15+ min early121 flights33.3%
- Within 15 min172 flights47.4%
- 15–29 min late26 flights7.2%
- 30–59 min late29 flights8.0%
- 1–2 hours late10 flights2.8%
- 2+ hours late5 flights1.4%
Scale runs 0% to 100%.
Share of 363 completed flights by arrival against schedule.
A late pushback is often recovered here: of 75 departures that left 15 minutes late or more, 27 still arrived on time. In the other direction, 22 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 IAH.
The worst days
Worst days for UA 668
The latest arrival of the period was on 14 December 2025, 6 hours 21 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 14 December 2025 | 6 hours 21 minutes | Late-arriving aircraft |
| 4 July 2026 | 3 hours 41 minutes | Late-arriving aircraft |
| 6 July 2026 | 3 hours 9 minutes | Late-arriving aircraft |
| 7 March 2026 | 2 hours 32 minutes | National Airspace System |
| 30 November 2025 | 2 hours 13 minutes | Late-arriving aircraft |
Delay causes
Why UA 668 runs late
Late-arriving aircraft accounts for 63% of the 3,635 delay minutes carriers reported here, and the remaining four split what is left.
- 63%Late-arriving aircraft
- 22%National Airspace System
- 14%Carrier
63% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 3,635 reported delay minutes here, that single category outweighs weather by 63 to one. The split is drawn from 3,635 delay minutes reported on UA 668.
Cancellations are rare at 0.27%, 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 4.1% 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 2,007 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.
Every one of the 365 flights under UA 668 in the data flew SJU to IAH. The number was not reused on any other city pair, which makes this a clean record of one route.
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 668
For a booking, UA 668 is one of the weaker ways to fly SJU to IAH: 8 points below the route as a whole. If the schedule allows, compare it with the other departures listed on the route page before settling on this one.
Related
Where to go next
- SJU to IAH, every carrier and departure
- IAH to SJU, the return direction
- United Airlines 1644 on the same route96.4%
- Luis Munoz Marin International (SJU) delay statistics
- George Bush Intercontinental (IAH) 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
- Why the first flight of the morning is statistically safest
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.