Best time to fly out of Luis Munoz Marin (SJU)

The early-flight folk wisdom holds up at Luis Munoz Marin: departures in the 6–8am band left on time 91% of the time, against 59.2% in the 10pm–12am band. These are historical odds, not forecasts. The records say what happened on this schedule over three years; they know nothing about tomorrow’s thunderstorm.

Data through June 2026 · Bureau of Transportation Statistics

On-time rate by hour and day

On this page, “on time” means a departure that pushed back less than 15 minutes behind its scheduled time — the Bureau of Transportation Statistics definition, and the one airlines are held to.

Share of departures that left on time, by hour band and day of week.
Departure time MonTueWedThuFriSatSun
Before 6am 76 76 80 83 80 81 80
6–8am 90 91 92 92 92 91 90
8–10am 87 88 89 88 89 88 89
10am–12pm 80 80 83 80 81 80 82
12–2pm 76 80 79 78 79 76 76
2–4pm 73 74 76 71 73 67 69
4–6pm 68 73 77 68 70 63 64
6–8pm 65 73 72 70 70 63 61
8–10pm 60 72 68 64 64 61 60
10pm–12am 60 58 60 65 61 61 52
fewer left on time more left on time

The steadiest stretch at SJU was 6–8am — 91% of departures left on time across 16,066 flights. The weakest was 10pm–12am at 59.2%. 6–8am departures from SJU left on time 91% of the time across 16,066 flights; 6–8pm departures, 67.6% across 10,288. That is a gap of 23.4 points, and it is the whole case for the early flight.

The year at SJU

August was the hard month at SJU: 68.6% of departures left on time, across 9,059 flights. April was the easy one at 81%. Each month pools three years of that month, so a single bad week does not decide it.

Share of departures that left on time, by calendar month. Best month in green, worst in amber. The hairline sits at the overall rate, 76.1%.
Departure on-time share at SJU by calendar month
Month Share departures that left on time Flights
January 72.3% 9,541
February 77.9% 8,333
March 73.9% 10,052
April 81% 9,232
May 80.3% 9,046
June 78.1% 9,691
July 68.8% 10,212
August 68.6% 9,059
September 80.5% 6,225
October 80.3% 6,801
November 80.7% 8,115
December 75.3% 9,967

Airlines at SJU

Every airline with at least 100 departures from SJU, busiest first. These are that airline’s departures from this airport only — its record across the country sits on its own page.

Airline Left on time Typical delay Cancelled Departures
JetBlue Airways 71.7% 84 min 1.3% 32,329
Frontier Airlines 71.5% 92 min 2.1% 16,180
American Airlines 77.3% 97 min 0.8% 13,099
Spirit Airlines 74.4% 77 min 2.1% 12,230
Southwest Airlines 78.8% 48 min 0.6% 11,708
Delta Air Lines 86.9% 77 min 0.8% 10,845
United Airlines 83.8% 81 min 1.2% 9,858

Spirit Airlines (through May 2026) stopped filing before June 2026. Its row covers a shorter run of months than the rest of the table, so its figure is not set against the others anywhere on this page.

What delays out of SJU were put down to

Airlines file a reason with every arrival running 15 minutes late or more. Across 24,735 flights that departed SJU and ran 15 minutes late or more, the delay minutes break down with 47.3% put down to late-arriving aircraft and 36.8% to airline operations.

Late-arriving aircraft 47.3% Airline operations 36.8% Air traffic & airport volume 14.4% Severe weather 1.3% Security 0.1%
  • Late-arriving aircraft 47.3%
  • Airline operations 36.8%
  • Air traffic & airport volume 14.4%
  • Severe weather 1.3%
  • Security 0.1%

Late-arriving aircraft is the knock-on category: the plane came in late, so it went out late again. It is why a 7am problem in Newark is still a problem in Denver at dinnertime, and why it is usually the biggest slice on the bar.

If you are connecting through SJU

Of 106,282 scheduled arrivals into SJU, 71.5% reached the gate less than 15 minutes behind schedule. Of the 28,690 arrivals that ran late, 53.3% were no more than 45 minutes behind — which is the difference between a tight connection and a new boarding pass.

Work out a specific layover — pick the airport and the minutes you have, and the tool reads the same arrival records back as a share.

Busiest routes out of SJU

Ranked by flights, with the share that arrived on time at the far end. Where a route carries enough flights for a page of its own the chip goes there; otherwise it goes to the destination airport.

SJU in one number

Luis Munoz Marin (SJU)

Rank 49 of 363 US airports by departures. Steadiest stretch of the day: 6–8am. Hardest month: August.

July 2023–June 2026 · 104,860 departures flown

76.1% of departures left on time

Questions about SJU

What is the best time of day to fly out of Luis Munoz Marin?
6–8am. Departures in that band left on time 91% of the time across 16,066 flights, July 2023 through June 2026 — the best of the ten bands in the day. The 10pm–12am band was the weakest at 59.2%.
Is the early flight out of SJU really more reliable?
6–8am departures from SJU left on time 91% of the time across 16,066 flights; 6–8pm departures, 67.6% across 10,288. That is a gap of 23.4 points, and it is the whole case for the early flight.
What is the worst month to fly out of SJU?
August: 68.6% of the departures that flew left on time, with 9,059 scheduled. April was the other end of the year at 81%. Each figure pools three years of that calendar month.
Which airline is most on time at SJU?
Delta Air Lines — 86.9% of its 10,845 departures from SJU left on time. Frontier Airlines sat at the other end at 71.5% over 16,180 flights. Only airlines with at least 100 departures here are ranked. Airlines that stopped filing before June 2026 are left out of the ranking — their figures cover a shorter run of months than the rest of the table.
How often are flights cancelled at SJU?
1.3% of scheduled departures were cancelled over July 2023 through June 2026. Cancellations are counted against everything scheduled, not against everything that flew — a rate that looks small still adds up to real people in a rebooking line.