Flight number record

UA 1831

United Airlines · Atlanta to Washington

Route: ATL → IAD
Departs: 14:40
Flights: 359
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 1831, check with United Airlines.

UA 1831 lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by close to two hours on average. That is a workable record, not a spotless one. That rests on 359 flights, with a median arrival 4 minutes early.

On time

77.2%

Arrivals under 15 minutes late, of 356 completed flights

Avg delay

109 min

Across delayed arrivals only, not all flights

Cancelled

0.56%

National rate is 1.81%

1 hour+ late

11.5%

National rate is 8.1%

These figures cover 359 flights between July 2025 and June 2026. Beyond the headline rate, 11.5% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.

Schedule

When UA 1831 flies

UA 1831 flies ATL to IAD without a single fixed slot. Its most common scheduled departure was 14:40, used on 121 of 359 flights, with 14:37 (68 flights) and 14:38 (46 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 14:40121 flights33.7%
Departs 14:3768 flights18.9%
Departs 14:3846 flights12.8%

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 14:40 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 72.4%, and UA 1831 runs 5 points better at 77.2%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

UA 1831 next to ATL to IAD

Every carrier on ATL to IAD combined arrived on time 76.5% of the time across 3,979 flights, so UA 1831 is about level with it. United flew 1,099 flights on the same city pair under all its flight numbers, including this one, and those ran 81.4% on time. Across its whole network United Airlines managed 79.0%, which this flight trails by 2 points.

UA 1831 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 1831thin sample	359	77.2%	109 min	0.56%	B+
All United Airlines on ATL–IAD	1,099	81.4%	83 min	0.55%	B+
All carriers on ATL–IAD	3,979	76.5%	81 min	1.99%	B
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 1831 quarter by quarter

UA 1831 did not run the same all year. Its best quarter was Apr–Jun 2026 at 84.6% on time and its weakest Jul–Sep 2025 at 70.5%, a swing of 14 points on roughly 90 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 202589 flights70.5%
Oct–Dec 202590 flights73.3%
Jan–Mar 202689 flights80.5%
Apr–Jun 202691 flights84.6%

Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.

By weekday, UA 1831 did best on Monday at 82.7% on time and worst on Sunday at 64.7%. Each day rests on about 51 flights, so a gap of 18 points is worth noticing but could still narrow in another year.

Delay causes

Why UA 1831 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 8,787 reported delay minutes.

Late-arriving aircraft
41%
National Airspace System
36%
Extreme weather
12%
Carrier
11%

Extreme weather accounts for 12% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.0 times the usual weather exposure. The split is drawn from 8,787 delay minutes reported on UA 1831.

Cancellations are rare at 0.56%, 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

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 11.5% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

The 534 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 three other city pairs in the data, including IAD to EWR (151), ORD to ATL (21) and PBI to EWR (3), but none flew often enough under UA 1831 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to ATL to IAD only.

One caution: this is a thin sample. 359 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 1831

For a booking, read UA 1831 as 77.2% on time with 0.56% cancelled over 359 flights. Those are rates from the past twelve months, not a forecast for any particular 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