Flight number record

AS 634

Alaska Airlines · Las Vegas to San Francisco

Route: LAS → SFO
Departs: 15:39
Flights: 280
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s AS 634, check with Alaska Airlines.

AS 634 draws a D+. Roughly one flight in two arrives at least 15 minutes late, and the typical late arrival is roughly 45 minutes behind schedule. Build slack into anything you connect to. That rests on 280 flights, with a median arrival 5 minutes late.

The national on-time rate over the same period is 77.6%, so AS 634 runs 18 points behind the country as a whole. Across a thousand flights that is about 185 extra late arrivals.

On time

59.1%

Arrivals under 15 minutes late, of 279 completed flights

Avg delay

47 min

Across delayed arrivals only, not all flights

Cancelled

0.36%

National rate is 1.81%

1 hour+ late

9.0%

National rate is 8.1%

These figures cover 280 flights between July 2025 and June 2026. Beyond the headline rate, 9.0% 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 AS 634 flies

AS 634 flies LAS to SFO without a single fixed slot. Its most common scheduled departure was 15:39, used on 94 of 280 flights, with 15:34 (35 flights) and 15:50 (28 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 15:3994 flights33.6%
Departs 15:3435 flights12.5%
Departs 15:5028 flights10.0%

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 15:39 departure sits in the 2pm–5pm window. Across every US flight scheduled in that window the on-time rate is 72.4%, and AS 634 runs 13 points worse at 59.1%. Midday slots inherit some of the morning's delays without yet carrying the full weight of the evening's.

Against the route

AS 634 next to LAS to SFO

Every carrier on LAS to SFO combined arrived on time 62.8% of the time across 6,060 flights, so AS 634 is 4 points behind it. Alaska flew 1,116 flights on the same city pair under all its flight numbers, including this one, and those ran 66.5% on time. Across its whole network Alaska Airlines managed 79.1%, which this flight trails by 20 points.

AS 634 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
AS 634thin sample	280	59.1%	47 min	0.36%	D+
All Alaska Airlines on LAS–SFO	1,116	66.5%	52 min	1.08%	C
All carriers on LAS–SFO	6,060	62.8%	59 min	0.68%	D+
Alaska Airlines, whole network	293,372	79.1%	52 min	1.28%	B

Across the year

AS 634 quarter by quarter

AS 634 did not run the same all year. Its best quarter was Jan–Mar 2026 at 81.2% on time and its weakest Apr–Jun 2026 at 34.1%, a swing of 47 points on roughly 70 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 202586 flights64.7%
Oct–Dec 202564 flights67.2%
Jan–Mar 202648 flights81.2%
Apr–Jun 202682 flights34.1%

Scale runs 25% to 85%. Rows with fewer than 30 flights show a dash.

By weekday, AS 634 did best on Saturday at 67.7% on time and worst on Sunday at 50.0%. Each day rests on about 40 flights, so a gap of 18 points is worth noticing but could still narrow in another year.

Delay causes

Why AS 634 runs late

One category carries most of the weight here. Late-arriving aircraft accounts for 49% of the 5,397 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.

Late-arriving aircraft
49%
National Airspace System
42%
Carrier
8%
Extreme weather
2%
Security
1%

49% 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 5,397 reported delay minutes here, that single category outweighs weather by 29 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 5,397 delay minutes reported on AS 634.

Cancellations are rare at 0.36%, 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

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.0% 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 one other city pair in the data, including SFO to LAS (63), but none flew often enough under AS 634 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to LAS to SFO only.

One caution: this is a thin sample. 280 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 AS 634

For a booking, read AS 634 as 59.1% on time with 0.36% cancelled over 280 flights. Those are rates from the past twelve months, not a forecast for any particular day.

Where to go next

A flight number here means Alaska 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