Flight number record

UA 1644

United Airlines · San Juan to Houston

Route: SJU → IAH
Departs: 07:00
Flights: 364
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 17 points better than the national rate of 77.6%. When something does go wrong the average delay runs about 55 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 17 points better than the US average of 77.6%. That gap is worth roughly 171 fewer late arrivals for every thousand flights.

On time

94.7%

Arrivals under 15 minutes late, of 361 completed flights

Avg delay

54 min

Across delayed arrivals only, not all flights

Cancelled

0.55%

National rate is 1.81%

1 hour+ late

1.4%

National rate is 8.1%

These figures cover 364 flights between July 2025 and June 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.

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. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 07:00211 flights58.0%
Departs 07:45101 flights27.7%

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 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 5 points better at 94.7%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

UA 1644 next to SJU to IAH

Every carrier on SJU to IAH combined arrived on time 87.7% of the time across 948 flights, so UA 1644 is 7 points ahead of it. United flew 872 flights on the same city pair under all its flight numbers, including this one, and those ran 88.9% on time. Across its whole network United Airlines managed 79.0%, which this flight beats by 16 points.

UA 1644 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 1644thin sample	364	94.7%	54 min	0.55%	A+
All United Airlines on SJU–IAH	872	88.9%	52 min	0.57%	A+
All carriers on SJU–IAH	948	87.7%	55 min	0.63%	A+
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 1644 quarter by quarter

Quarter by quarter UA 1644 held fairly steady: 91.2% in Jul–Sep 2025, 94.6% in Oct–Dec 2025, 95.4% in Jan–Mar 2026 and 97.8% in Apr–Jun 2026. A spread of 7 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202592 flights91.2%
Oct–Dec 202592 flights94.6%
Jan–Mar 202689 flights95.4%
Apr–Jun 202691 flights97.8%

Scale runs 85% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, UA 1644 ranged from 88.5% on Thursday to 98.0% on Monday. With about 52 flights behind each day, a spread of 10 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why UA 1644 runs late

One category carries most of the weight here. Carrier accounts for 53% of the 1,031 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.

Carrier
53%
Late-arriving aircraft
31%
National Airspace System
16%

The largest share of delay minutes, 53%, 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 549 of the 1,031 delay minutes reported here. The split is drawn from 1,031 delay minutes reported on UA 1644.

Cancellations are rare at 0.55%, 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

Badly late arrivals are rare here: only 1.4% land an hour or more behind schedule, against 8.1% 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: 94.7% on time and 0.55% cancelled. That is a base rate, not a promise about any single 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