Flight number record
UA 688
United Airlines · Washington to Boston
- Route
- IAD → BOS
- Departs
- 17:10
- Flights
- 362
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 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 a little over an hour behind schedule. Build slack into anything you connect to. That rests on 362 flights, with a median arrival 4 minutes late.
The national on-time rate over the same period is 77.3%, so UA 688 runs 16 points behind the country as a whole. Across a thousand flights that is about 159 extra late arrivals.
Key figures
On time
61.4%
Arrivals under 15 minutes late, of 350 completed flights
Avg delay
79 min
Across delayed arrivals only, not all flights
Cancelled
3.31%
National rate is 1.89%
1 hour+ late
19.4%
National rate is 8.3%
These figures cover 362 flights between September 2025 and August 2026. Beyond the headline rate, 19.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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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 117 of 362 flights, with 17:25 (82 flights) and 17:16 (55 flights) next.
- Departs 17:10117 flights32.3%
- Departs 17:2582 flights22.7%
- Departs 17:1655 flights15.2%
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 17:10 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and UA 688 runs 7 points worse at 61.4%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
UA 688 next to IAD to BOS
Every carrier on IAD to BOS combined arrived on time 76.9% of the time across 1,524 flights, so UA 688 is 16 points behind it. United flew 1,447 flights on the same city pair under all its flight numbers, including this one, and those ran 77.1% on time. Across its whole network United Airlines managed 78.8%, which this flight trails by 17 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 688thin sample | 362 | 61.4% | 79 min | 3.31% | D− |
| All United Airlines on IAD–BOS | 1,447 | 77.1% | 70 min | 2.07% | B |
| All carriers on IAD–BOS | 1,524 | 76.9% | 70 min | 2.76% | B |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | 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 Oct–Dec 2025 at 56.8%, a swing of 21 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 202530 flights—
- Oct–Dec 202590 flights56.8%
- Jan–Mar 202689 flights78.0%
- Apr–Jun 202691 flights57.8%
- Jul–Sep 202662 flights65.6%
Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.
By weekday, UA 688 did best on Saturday at 79.2% on time and worst on Sunday at 52.1%. Each day rests on about 52 flights, so a gap of 27 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 688 runs when it is late
When UA 688 is late it tends to be very late: 68 of its 135 late arrivals were an hour or more behind, and 28 were two hours or more.
- 15+ min early60 flights17.1%
- Within 15 min155 flights44.3%
- 15–29 min late32 flights9.1%
- 30–59 min late35 flights10.0%
- 1–2 hours late40 flights11.4%
- 2+ hours late28 flights8.0%
Scale runs 0% to 100%.
Share of 350 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 118 departures that left 15 minutes late or more, only 7 made it up before arrival. In the other direction, 24 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at BOS.
The worst days
Worst days for UA 688
The latest arrival of the period was on 20 May 2026, 9 hours 47 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. Three of the five worst days fell in August 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 20 May 2026 | 9 hours 47 minutes | Late-arriving aircraft |
| 21 July 2026 | 6 hours 1 minute | National Airspace System |
| 7 August 2026 | 3 hours 48 minutes | National Airspace System |
| 10 August 2026 | 3 hours 32 minutes | Late-arriving aircraft |
| 6 August 2026 | 3 hours 27 minutes | Late-arriving aircraft |
Delay causes
Why UA 688 runs late
National Airspace System accounts for 70% of the 11,000 delay minutes carriers reported here, and the remaining four split what is left.
- 70%National Airspace System
- 15%Late-arriving aircraft
- 8%Carrier
- 7%Extreme weather
70% 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 7,463 minutes out of 11,000, against a national NAS share of 21%. The split is drawn from 10,718 delay minutes reported on UA 688.
Cancellations run at 3.31%, against 1.89% nationally. That is about 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
19.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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 SLC to IAD (74), LAS to IAD (53) and LAX to IAD (51), 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: 3.31% of its 362 scheduled flights did not operate. A late arrival costs a little over an hour, but a cancellation costs the day, so leave a later option open.
Related
Where to go next
- IAD to BOS, every carrier and departure
- BOS to IAD, the return direction
- United Airlines 641 on the same route92.3%
- United Airlines 755 on the same route79.1%
- Washington Dulles International (IAD) delay statistics
- Boston Logan International (BOS) 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
- What a cancellation rate actually tells you (and what it hides)
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.