Flight number record

UA 558

United Airlines · Denver to Boston

Route: DEN → BOS
Departs: 07:45
Flights: 340
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 558, check with United Airlines.

UA 558 earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 13 points better than the national rate of 77.6%. When something does go wrong the average delay runs about 50 minutes. That rests on 340 flights, with a median arrival 13 minutes early.

Set against the rest of the country, UA 558's record is 13 points better than the US average of 77.6%. That gap is worth roughly 129 fewer late arrivals for every thousand flights.

On time

90.5%

Arrivals under 15 minutes late, of 336 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

0.59%

National rate is 1.81%

1 hour+ late

1.8%

National rate is 8.1%

These figures cover 340 flights between July 2025 and June 2026. The median arrival is 13 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Schedule

When UA 558 flies

UA 558 flies DEN to BOS without a single fixed slot. Its most common scheduled departure was 07:45, used on 94 of 340 flights, with 08:05 (68 flights) and 08:01 (58 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 07:4594 flights27.6%
Departs 08:0568 flights20.0%
Departs 08:0158 flights17.1%

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 07:45 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and UA 558 runs level with that at 90.5%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

UA 558 next to DEN to BOS

Every carrier on DEN to BOS combined arrived on time 71.4% of the time across 3,903 flights, so UA 558 is 19 points ahead of it. United flew 1,911 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 79.0%, which this flight beats by 12 points.

UA 558 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 558thin sample	340	90.5%	49 min	0.59%	A+
All United Airlines on DEN–BOS	1,911	77.1%	70 min	0.84%	B+
All carriers on DEN–BOS	3,903	71.4%	70 min	1.18%	C
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 558 quarter by quarter

UA 558 did not run the same all year. Its best quarter was Apr–Jun 2026 at 96.7% on time and its weakest Oct–Dec 2025 at 83.8%, a swing of 13 points on roughly 85 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 flights89.1%
Oct–Dec 202581 flights83.8%
Jan–Mar 202676 flights91.9%
Apr–Jun 202691 flights96.7%

Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, UA 558 ranged from 86.5% on Sunday to 94.1% on Friday. With about 49 flights behind each day, a spread of 8 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why UA 558 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 1,579 reported delay minutes.

National Airspace System
41%
Late-arriving aircraft
35%
Carrier
25%

35% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 1,579 reported delay minutes here, that single category outweighs weather by 35 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 1,579 delay minutes reported on UA 558.

Cancellations are rare at 0.59%, 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

Badly late arrivals are rare here: only 1.8% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

At 1,754 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.

The same number turns up on one other city pair in the data, including BOS to EWR (32), but none flew often enough under UA 558 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to DEN to BOS only.

One caution: this is a thin sample. 340 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 558

For a booking, UA 558 has one of the better records a US domestic flight can show: 90.5% on time and 0.59% cancelled. That is a base rate, not a promise about any single 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