Flight number record
UA 1644
United Airlines · San Juan to Houston
- Route
- SJU → IAH
- Departs
- 07:00
- Flights
- 364
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 1644, check with United Airlines.
UA 1644 earns an A+. Nearly every flight arrives inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 19 points better than the national rate of 77.3%. When something does go wrong the average delay runs about 45 minutes. That rests on 364 flights, with a median arrival 19 minutes early.
Set against the rest of the country, UA 1644's record is 19 points better than the US average of 77.3%. That gap is worth roughly 191 fewer late arrivals for every thousand flights.
Key figures
On time
96.4%
Arrivals under 15 minutes late, of 362 completed flights
Avg delay
45 min
Across delayed arrivals only, not all flights
Cancelled
0.55%
National rate is 1.89%
1 hour+ late
0.6%
National rate is 8.3%
These figures cover 364 flights between September 2025 and August 2026. The median arrival is 19 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 1644 flies
UA 1644 flies SJU to IAH without a single fixed slot. Its most common scheduled departure was 07:00, used on 211 of 364 flights, with 07:45 (101 flights) next.
- Departs 07:00211 flights58.0%
- Departs 07:45101 flights27.7%
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 07:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and UA 1644 runs 7 points better at 96.4%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
UA 1644 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 1644 is 8 points ahead of 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 18 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 1644thin sample | 364 | 96.4% | 45 min | 0.55% | A+ |
| 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 1644 quarter by quarter
Quarter by quarter UA 1644 held fairly steady: 100.0% in Jul–Sep 2025, 94.6% in Oct–Dec 2025, 95.4% in Jan–Mar 2026, 97.8% in Apr–Jun 2026 and 96.8% in Jul–Sep 2026. A spread of 5 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202530 flights100.0%
- Oct–Dec 202592 flights94.6%
- Jan–Mar 202689 flights95.4%
- Apr–Jun 202691 flights97.8%
- Jul–Sep 202662 flights96.8%
Scale runs 85% to 100%.
By weekday, UA 1644 ranged from 88.5% on Thursday to 100.0% on Wednesday. With about 52 flights behind each day, a spread of 12 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late UA 1644 runs when it is late
UA 1644 often beats the schedule: 222 of 362 completed flights, 61%, arrived 15 minutes or more early. Most of the lateness is short. 7 of the 13 late arrivals were under half an hour behind, and 2 reached an hour or more.
- 15+ min early222 flights61.3%
- Within 15 min127 flights35.1%
- 15–29 min late7 flights1.9%
- 30–59 min late4 flights1.1%
- 1–2 hours late1 flights0.3%
- 2+ hours late1 flights0.3%
Scale runs 0% to 100%.
Share of 362 completed flights by arrival against schedule.
Only 15 of 362 completed flights left 15 minutes late or more, too few to say how often the time is made up.
The worst days
Worst days for UA 1644
The latest arrival of the period was on 21 February 2026, 3 hours 29 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 21 February 2026 | 3 hours 29 minutes | Carrier |
| 12 March 2026 | 1 hour 18 minutes | Carrier |
| 9 June 2026 | 59 minutes | National Airspace System |
| 9 November 2025 | 36 minutes | Carrier |
| 27 November 2025 | 31 minutes | Carrier |
Delay causes
Why UA 1644 runs late
Carrier accounts for 77% of the 581 delay minutes carriers reported here, and the remaining four split what is left.
- 77%Carrier
- 23%National Airspace System
The largest share of delay minutes, 77%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 445 of the 581 delay minutes reported here. The split is drawn from 581 delay minutes reported on UA 1644.
Cancellations are rare at 0.55%, 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 0.6% 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 364 flights under UA 1644 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. 364 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 1644
For a booking, UA 1644 has one of the better records a US domestic flight can show: 96.4% on time and 0.55% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- SJU to IAH, every carrier and departure
- IAH to SJU, the return direction
- United Airlines 668 on the same route80.7%
- 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
- 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.