Flight number record
UA 2173
United Airlines · Boise to Denver
- Route
- BOI → DEN
- Departs
- 14:40
- Flights
- 364
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 2173, check with United Airlines.
UA 2173 lands a B+, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by close to two hours on average. That rests on 364 flights, with a median arrival 4 minutes early.
Key figures
On time
76.3%
Arrivals under 15 minutes late, of 359 completed flights
Avg delay
105 min
Across delayed arrivals only, not all flights
Cancelled
0.27%
National rate is 1.89%
1 hour+ late
11.4%
National rate is 8.3%
These figures cover 364 flights between September 2025 and August 2026. Beyond the headline rate, 11.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Schedule
When UA 2173 flies
UA 2173 flies BOI to DEN without a single fixed slot. Its most common scheduled departure was 14:40, used on 112 of 364 flights, with 14:37 (69 flights) next.
- Departs 14:40112 flights30.8%
- Departs 14:3769 flights19.0%
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 14:40 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 71.9%, and UA 2173 runs 4 points better at 76.3%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.
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Against the route
UA 2173 next to BOI to DEN
Every carrier on BOI to DEN combined arrived on time 81.7% of the time across 3,034 flights, so UA 2173 is 5 points behind it. United flew 919 flights on the same city pair under all its flight numbers, including this one, and those ran 80.7% on time. Across its whole network United Airlines managed 78.8%, which this flight trails by 3 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 2173thin sample | 364 | 76.3% | 105 min | 0.27% | B+ |
| All United Airlines on BOI–DEN | 919 | 80.7% | 103 min | 0.22% | B+ |
| All carriers on BOI–DEN | 3,034 | 81.7% | 82 min | 0.13% | B+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 2173 quarter by quarter
UA 2173 did not run the same all year. Its best quarter was Jan–Mar 2026 at 85.6% on time and its weakest Jul–Sep 2026 at 58.3%, a swing of 27 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 202591 flights80.2%
- Jan–Mar 202690 flights85.6%
- Apr–Jun 202691 flights79.8%
- Jul–Sep 202662 flights58.3%
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
By weekday, UA 2173 did best on Tuesday at 87.8% on time and worst on Friday at 68.6%. Each day rests on about 52 flights, so a gap of 19 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 2173 runs when it is late
The 85 late arrivals split 31 under half an hour, 13 between 30 and 60 minutes, and 41 an hour or more.
- 15+ min early86 flights24.0%
- Within 15 min188 flights52.4%
- 15–29 min late31 flights8.6%
- 30–59 min late13 flights3.6%
- 1–2 hours late17 flights4.7%
- 2+ hours late24 flights6.7%
Scale runs 0% to 100%.
Share of 359 completed flights by arrival against schedule.
13 of 75 late departures made up the time and arrived on time, 17% of them. In the other direction, 23 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 DEN.
The worst days
Worst days for UA 2173
The latest arrival of the period was on 17 April 2026, 20 hours 10 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 17 April 2026 | 20 hours 10 minutes | Carrier |
| 8 June 2026 | 7 hours 42 minutes | Carrier |
| 13 June 2026 | 7 hours 30 minutes | Carrier |
| 1 August 2026 | 5 hours 44 minutes | Late-arriving aircraft |
| 22 August 2026 | 5 hours 39 minutes | National Airspace System |
Delay causes
Why UA 2173 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 8,930 reported delay minutes.
- 38%National Airspace System
- 31%Carrier
- 30%Late-arriving aircraft
- 1%Extreme weather
38% 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 3,422 minutes out of 8,930, against a national NAS share of 21%. The split is drawn from 8,930 delay minutes reported on UA 2173.
Cancellations are rare at 0.27%, below the national 1.89% 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
11.4% 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 649 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 one other city pair in the data, including DEN to HDN (155), but none flew often enough under UA 2173 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to BOI to DEN only.
One caution: this is a thin sample. 364 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 2173
For a booking, UA 2173 is one of the weaker ways to fly BOI to DEN: 5 points below the route as a whole. If the schedule allows, compare it with the other departures listed on the route page before settling on this one.
Related
Where to go next
- BOI to DEN, every carrier and departure
- DEN to BOI, the return direction
- United Airlines 1782 on the same route91.1%
- SkyWest Airlines 5924 on the same route90.7%
- Denver International (DEN) 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
- How often a connection fails at the major US hubs
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.