Flight number record

UA 637

United Airlines · Washington to Austin

Route: IAD → AUS
Departs: 08:25
Flights: 265
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 637, check with United Airlines.

UA 637 earns an A+. Nearly every flight arrives inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 16 points better than the national rate of 77.6%. When something does go wrong the average delay runs about 40 minutes. That rests on 265 flights, with a median arrival 16 minutes early.

Set against the rest of the country, UA 637's record is 16 points better than the US average of 77.6%. That gap is worth roughly 160 fewer late arrivals for every thousand flights.

On time

93.6%

Arrivals under 15 minutes late, of 264 completed flights

Avg delay

41 min

Across delayed arrivals only, not all flights

Cancelled

0.38%

National rate is 1.81%

1 hour+ late

1.5%

National rate is 8.1%

These figures cover 265 flights between July 2025 and June 2026. The median arrival is 16 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 637 flies

UA 637 flies IAD to AUS without a single fixed slot. Its most common scheduled departure was 08:25, used on 58 of 265 flights, with 08:45 (42 flights) and 08:15 (40 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 08:2558 flights21.9%
Departs 08:4542 flights15.8%
Departs 08:1540 flights15.1%

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 08:25 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 84.1%, and UA 637 runs 10 points better at 93.6%. 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 637 next to IAD to AUS

Every carrier on IAD to AUS combined arrived on time 83.9% of the time across 1,049 flights, so UA 637 is 10 points ahead of it. United flew 1,007 flights on the same city pair under all its flight numbers, including this one, and those ran 84.2% on time. Across its whole network United Airlines managed 79.0%, which this flight beats by 15 points.

UA 637 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 637thin sample	265	93.6%	41 min	0.38%	A+
All United Airlines on IAD–AUS	1,007	84.2%	67 min	0.79%	B+
All carriers on IAD–AUS	1,049	83.9%	66 min	0.76%	B+
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 637 quarter by quarter

Quarter by quarter UA 637 held fairly steady: 91.7% in Jul–Sep 2025, 93.8% in Oct–Dec 2025, 93.2% in Jan–Mar 2026 and 96.4% in Apr–Jun 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 202584 flights91.7%
Oct–Dec 202581 flights93.8%
Jan–Mar 202645 flights93.2%
Apr–Jun 202655 flights96.4%

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

By weekday, UA 637 ranged from 90.9% on Monday to 97.7% on Thursday. With about 38 flights behind each day, a spread of 7 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why UA 637 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 696 reported delay minutes.

National Airspace System
42%
Carrier
27%
Late-arriving aircraft
25%
Extreme weather
6%

42% 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 292 minutes out of 696, against a national NAS share of 21%. The split is drawn from 696 delay minutes reported on UA 637.

Cancellations are rare at 0.38%, 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 1.5% 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.

The 1,297 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The same number turns up on seven other city pairs in the data, including AUS to LAX (77), PWM to ORD (35) and SYR to IAD (20), but none flew often enough under UA 637 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to IAD to AUS only.

One caution: this is a thin sample. 265 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 637

For a booking, UA 637 has one of the better records a US domestic flight can show: 93.6% on time and 0.38% 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