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Flight Reliability

WN 1521 · Southwest Airlines

This number covered several routes in this period.

One number, several routes.

Airlines reuse flight numbers, and WN 1521 moved between routes during this period. Numbers below combine all of them, so treat them as background, not a verdict. For a cleaner answer, check the route you are actually flying.

Combined across all its routes

78%
Arrive within 15 minutes
4 min
Average arrival delay
0.9%
Cancelled
5 min early
Median arrival delay

Based on 333 historical flights. Data through May 2026.

The breakdown

On-time by weekday
  • Mon78%(51 flights)
  • Tue72%(43 flights)
  • Wed82%(44 flights)
  • Thu82%(51 flights)
  • Fri75%(51 flights)
  • Sat86%(44 flights)
  • Sun70%(46 flights)
On-time by departure window
  • 3–6 AM—(4 flights)
  • 6–9 AM93%(75 flights)
  • 9 AM–12 PM64%(52 flights)
  • 12–3 PM73%(48 flights)
  • 3–6 PM67%(70 flights)
  • 6–9 PM65%(17 flights)
  • 9 PM–12 AM91%(64 flights)
On-time trend by month
60%
May

Jun 74% → May 60% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202574%19
July 202547%19
August 202566%35
September 202585%39
October 202596%22
November 202576%29
December 202577%31
January 202690%31
February 2026100%28
March 202679%19
April 202679%28
May 202660%30
Departures on time
73%
Diverted
0%
Flights flown
330
Months covered
12

Keep nerding

Based on 333 historical flights, because apparently we checked. Historical flight data: U.S. Bureau of Transportation Statistics, June 2025 – May 2026. Data through May 2026. How we calculate this.