Airport month record

SEAMAY

Seattle-Tacoma International in May 2026

Departures: 14,564
Month: May 2026
National, same month: 78.6%
Carriers: 9

Historical statistics for May 2026, not live status or a forecast for this year’s May. For today’s conditions at SEA, see live FAA status.

SEA in May lands a B+, 4 points better than the national rate of 78.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 14,564 flights, of which SkyWest Airlines flew 2,577 at 86.1% on time.

SkyWest Airlines is the most reliable of the six carriers covered here at 86.1% on time across 2,577 flights.

On time

82.2%

Arrivals under 15 minutes late, of 14,458 completed departures

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

0.41%

Nationally in May: 0.92%

Whole year

79.4%

SEA across all twelve months

These figures cover 14,564 departures from Seattle-Tacoma International in May 2026. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.

Against the year

May next to SEA's other months

Against SEA's own year, May ran 3 points better than the twelve-month rate of 79.4%, which makes it number five of twelve months, best first. Cancellations were unusually low for SEA in May, at 0.41% against 0.99% across the year. Either side of it, April ran 85.6% on time and June 78.1%, so this month sits in line with its neighbours.

SEA month by month
Month	Flights	On time	Avg delay	Cancelled	Grade
July 2025	16,577	69.2%	57 min	1.38%	C
August 2025	15,970	73.6%	51 min	0.66%	C+
September 2025	14,552	82.9%	50 min	0.29%	B+
October 2025	13,859	82.9%	58 min	1.16%	B
November 2025	12,616	81.9%	58 min	1.69%	B
December 2025	13,023	74.0%	59 min	1.02%	C
January 2026	11,927	81.6%	60 min	1.91%	B
February 2026	11,000	84.4%	56 min	0.78%	B+
March 2026	12,830	80.2%	64 min	2.23%	B
April 2026	12,864	85.6%	56 min	0.17%	A+
May 2026 (this page)	14,564	82.2%	52 min	0.41%	B+
June 2026	15,402	78.1%	57 min	0.48%	B+

Departure window

The best time of day to leave SEA in May

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 12 points, against 16 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am1,681 flights89.9%
8am–11am3,107 flights84.9%
11am–2pm2,837 flights80.6%
2pm–5pm2,079 flights79.9%
5pm–8pm2,027 flights78.0%
8pm–5am2,833 flights81.1%

Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 89.9% of the time, against 78.0% for the evening window. That is 12 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 3,107 flights scheduled in it.

Across the week, Saturday is the strongest day at 84.9% on time and Thursday the weakest at 77.5%. 7 points is a smaller lever than departure hour, but it is free.

Carrier by carrier

Which airlines ran best at SEA in May

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 86.1% of the time; Southwest Airlines manages 70.2%. Sample sizes sit next to every figure, because a two-point gap across 610 flights means less than a ten-point one.

Carriers at SEA in May 2026
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlines	6,823	83.0%	45 min	0.38%	B+
Delta Air Lines	2,857	82.8%	60 min	0.60%	B+
SkyWest Airlines	2,577	86.1%	51 min	0.04%	A+
United Airlines	816	74.9%	64 min	0.74%	C+
American Airlines	630	76.7%	74 min	1.11%	B
Southwest Airlines	610	70.2%	44 min	0.33%	C+
Envoy Airthin sample	114	81.4%	89 min	0.00%	B+
Frontier Airlinesthin sample	100	87.0%	141 min	0.00%	A+
JetBlue Airwaysthin sample	37	52.8%	31 min	2.70%	F

The spread between SkyWest and Southwest is 16 points, wide enough that it should decide the booking. On a hundred trips that is 16 more arrivals inside the on-time window.

Route by route

Busiest routes out of SEA in May

Routes from SEA in May 2026
Route	Flights	On time	Avg delay	Cancelled	Grade
SEA to LAX · Los Angeles	677	86.8%	62 min	0.15%	A+
SEA to PHX · Phoenix	623	82.7%	48 min	0.32%	B+
SEA to SFO · San Francisco	591	40.7%	54 min	1.35%	F
SEA to ANC · Anchorage	587	79.2%	44 min	0.17%	B+
SEA to ORD · Chicago	562	81.3%	60 min	0.00%	B+
SEA to DEN · Denver	546	82.6%	41 min	0.18%	B+
SEA to LAS · Las Vegas	497	78.9%	66 min	0.80%	B+
SEA to DFW · Dallas-Fort Worth	482	78.5%	57 min	1.45%	B
SEA to SAN · San Diego	427	83.2%	45 min	0.94%	B+
SEA to GEG · Spokane	414	88.1%	68 min	0.24%	A+
SEA to PDX · Portland	391	84.4%	47 min	0.00%	B+
SEA to SMF · Sacramento	389	85.3%	50 min	0.00%	A+
SEA to BOI · Boisethin sample	363	87.9%	46 min	0.00%	A+
SEA to SJC · San Josethin sample	355	86.4%	49 min	0.28%	A+
SEA to SNA · Santa Anathin sample	353	92.9%	42 min	0.28%	A+
SEA to SLC · Salt Lake Citythin sample	338	85.2%	47 min	0.30%	A+
SEA to ATL · Atlantathin sample	298	82.8%	98 min	0.00%	B+
SEA to JFK · New Yorkthin sample	263	82.0%	80 min	1.90%	B
SEA to BOS · Bostonthin sample	254	83.0%	39 min	0.39%	B+
SEA to ONT · Ontariothin sample	249	86.2%	42 min	0.80%	A+
SEA to HNL · Honoluluthin sample	247	72.2%	46 min	0.81%	C+
SEA to MSP · Minneapolisthin sample	225	92.4%	46 min	0.89%	A+
SEA to EWR · Newarkthin sample	213	88.2%	48 min	0.00%	A+
SEA to DTW · Detroitthin sample	204	87.0%	95 min	0.49%	A+
SEA to IAD · Washingtonthin sample	202	86.0%	37 min	0.00%	A+

Delay causes

What held SEA up in May

One category carries most of the weight here. Carrier accounts for 45% of the 134,000 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.

Carrier
45%
Late-arriving aircraft
28%
National Airspace System
25%
Extreme weather
3%
Security
0%

The largest share of delay minutes, 45%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 60,000 of the 134,000 delay minutes reported here. The split is drawn from 134,241 reported delay minutes.

Cancellations are rare at 0.41%, below the national 0.92% 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.

Badly late arrivals are rare here: only 4.0% land an hour or more behind schedule, against 7.1% 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.

What to do with this

Flying from SEA in May

For a May trip through SEA: expect 82.2% on time and 0.41% cancelled, going by May 2026. The 5am–8am window was the strongest part of the day.

Seattle-Tacoma International (SEA), the whole year
SEA in July69.2%
SEA in August73.6%
SEA in September82.9%
SEA in October82.9%
SEA in November81.9%
SEA in December74.0%
SEA in January81.6%
SEA in February84.4%
SEA in March80.2%
SEA in April85.6%
SEA in June78.1%

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