Flight number record
UA 1240
United Airlines · Dallas-Fort Worth to Washington
- Route
- DFW → IAD
- Departs
- 17:15
- Flights
- 328
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 1240, check with United Airlines.
UA 1240 lands a B, level with the national rate of 77.3%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 328 flights, with a median arrival 4 minutes early.
Key figures
On time
77.5%
Arrivals under 15 minutes late, of 324 completed flights
Avg delay
75 min
Across delayed arrivals only, not all flights
Cancelled
1.22%
National rate is 1.89%
1 hour+ late
11.1%
National rate is 8.3%
These figures cover 328 flights between September 2025 and August 2026. Beyond the headline rate, 11.1% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When UA 1240 flies
UA 1240 flies DFW to IAD without a single fixed slot. Its most common scheduled departure was 17:15, used on 76 of 328 flights, with 17:22 (57 flights) and 17:25 (52 flights) next.
- Departs 17:1576 flights23.2%
- Departs 17:2257 flights17.4%
- Departs 17:2552 flights15.9%
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 17:15 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and UA 1240 runs 10 points better at 77.5%. 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 1240 next to DFW to IAD
Every carrier on DFW to IAD combined arrived on time 77.4% of the time across 1,962 flights, so UA 1240 is about level with it. United flew 929 flights on the same city pair under all its flight numbers, including this one, and those ran 83.6% on time. Across its whole network United Airlines managed 78.8%, close to this flight's figure.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 1240thin sample | 328 | 77.5% | 75 min | 1.22% | B |
| All United Airlines on DFW–IAD | 929 | 83.6% | 80 min | 0.86% | B+ |
| All carriers on DFW–IAD | 1,962 | 77.4% | 77 min | 1.73% | B |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 1240 quarter by quarter
UA 1240 did not run the same all year. Its best quarter was Jul–Sep 2025 at 90.0% on time and its weakest Jul–Sep 2026 at 65.6%, a swing of 24 points on roughly 66 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 flights90.0%
- Oct–Dec 202571 flights76.1%
- Jan–Mar 202674 flights86.1%
- Apr–Jun 202691 flights75.6%
- Jul–Sep 202662 flights65.6%
Scale runs 55% to 95%.
By weekday, UA 1240 did best on Wednesday at 84.0% on time and worst on Sunday at 66.7%. Each day rests on about 47 flights, so a gap of 17 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 1240 runs when it is late
The 73 late arrivals split 20 under half an hour, 17 between 30 and 60 minutes, and 36 an hour or more.
- 15+ min early57 flights17.6%
- Within 15 min194 flights59.9%
- 15–29 min late20 flights6.2%
- 30–59 min late17 flights5.2%
- 1–2 hours late27 flights8.3%
- 2+ hours late9 flights2.8%
Scale runs 0% to 100%.
Share of 324 completed flights by arrival against schedule.
A late pushback is often recovered here: of 78 departures that left 15 minutes late or more, 27 still arrived on time. In the other direction, 22 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 IAD.
The worst days
Worst days for UA 1240
The latest arrival of the period was on 24 May 2026, 6 hours 40 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On four of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 24 May 2026 | 6 hours 40 minutes | Carrier |
| 18 June 2026 | 4 hours 34 minutes | Late-arriving aircraft |
| 9 August 2026 | 4 hours 2 minutes | Late-arriving aircraft |
| 18 October 2025 | 3 hours 49 minutes | Late-arriving aircraft |
| 18 July 2026 | 3 hours 23 minutes | Late-arriving aircraft |
Delay causes
Why UA 1240 runs late
Late-arriving aircraft accounts for 47% of the 5,494 delay minutes carriers reported here, and the remaining four split what is left.
- 47%Late-arriving aircraft
- 26%Carrier
- 24%National Airspace System
- 3%Extreme weather
47% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,494 reported delay minutes here, that single category outweighs weather by 15 to one. The split is drawn from 5,494 delay minutes reported on UA 1240.
Cancellations sit at 1.22% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and routes
What a delay on this flight costs
11.1% 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 1,172 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.
The same number turns up on two other city pairs in the data, including ORD to FCA (19) and SFO to EWR (1), but none flew often enough under UA 1240 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to DFW to IAD only.
One caution: this is a thin sample. 328 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 1240
For a booking, read UA 1240 as 77.5% on time with 1.22% cancelled over 328 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- DFW to IAD, every carrier and departure
- IAD to DFW, the return direction
- United Airlines 358 on the same route83.6%
- United Airlines 2639 on the same route90.6%
- Dallas/Fort Worth International (DFW) delay statistics
- Washington Dulles International (IAD) 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
- Why the first flight of the morning is statistically safest
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.