Flight number record

UA 688

United Airlines · Washington to Boston

Route: IAD → BOS
Departs: 17:10
Flights: 362
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 688, check with United Airlines.

UA 688 draws a D−. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is an hour and a half behind schedule. Build slack into anything you connect to. That rests on 362 flights, with a median arrival 5 minutes late.

The national on-time rate over the same period is 77.6%, so UA 688 runs 17 points behind the country as a whole. Across a thousand flights that is about 172 extra late arrivals.

On time

60.4%

Arrivals under 15 minutes late, of 351 completed flights

Avg delay

88 min

Across delayed arrivals only, not all flights

Cancelled

3.04%

National rate is 1.81%

1 hour+ late

19.9%

National rate is 8.1%

These figures cover 362 flights between July 2025 and June 2026. Beyond the headline rate, 19.9% 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 688 flies

UA 688 flies IAD to BOS without a single fixed slot. Its most common scheduled departure was 17:10, used on 168 of 362 flights, with 17:16 (66 flights) and 17:25 (41 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 17:10168 flights46.4%
Departs 17:1666 flights18.2%
Departs 17:2541 flights11.3%

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 17:10 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and UA 688 runs 8 points worse at 60.4%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.

Against the route

UA 688 next to IAD to BOS

Every carrier on IAD to BOS combined arrived on time 77.3% of the time across 1,462 flights, so UA 688 is 17 points behind it. United flew 1,459 flights on the same city pair under all its flight numbers, including this one, and those ran 77.4% on time. Across its whole network United Airlines managed 79.0%, which this flight trails by 19 points.

UA 688 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 688thin sample	362	60.4%	88 min	3.04%	D−
All United Airlines on IAD–BOS	1,459	77.4%	73 min	1.92%	B
All carriers on IAD–BOS	1,462	77.3%	73 min	1.92%	B
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 688 quarter by quarter

UA 688 did not run the same all year. Its best quarter was Jan–Mar 2026 at 78.0% on time and its weakest Jul–Sep 2025 at 50.5%, a swing of 28 points on roughly 91 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 202592 flights50.5%
Oct–Dec 202590 flights56.8%
Jan–Mar 202689 flights78.0%
Apr–Jun 202691 flights57.8%

Scale runs 40% to 85%. Rows with fewer than 30 flights show a dash.

By weekday, UA 688 did best on Saturday at 75.5% on time and worst on Sunday at 47.9%. Each day rests on about 52 flights, so a gap of 28 points is worth noticing but could still narrow in another year.

Delay causes

Why UA 688 runs late

One category carries most of the weight here. National Airspace System accounts for 60% of the 12,000 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.

National Airspace System
60%
Late-arriving aircraft
21%
Carrier
9%
Extreme weather
9%

60% 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 7,408 minutes out of 12,000, against a national NAS share of 21%. The split is drawn from 12,249 delay minutes reported on UA 688.

Cancellations run at 3.04%, against 1.81% nationally. That is roughly one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

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. 19.9% 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 same number turns up on seven other city pairs in the data, including LAX to IAD (113), SLC to IAD (74) and LAS to IAD (53), but none flew often enough under UA 688 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to IAD to BOS only.

One caution: this is a thin sample. 362 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 688

For a booking, the cancellation rate is the figure to plan around on UA 688: 3.04% of its 362 scheduled flights did not operate. A late arrival costs an hour and a half, but a cancellation costs the day, so leave a later option open.

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