Skip to content
WanderNerd
Check a flight

Flight Reliability

DL 4042 · Delta Air Lines

Ontario → Seattle (ONT–SEA)85% of its flights flew this route. The rest (PSP–SLC, SLC–PSP) are included in these numbers.

100
Nerd Approved
WanderNerd Reliability Score
95%
Arrive within 15 minutes
4 min early
Average arrival delay
0%
Cancelled
9 min early
Median arrival delay

Based on 373 historical flights. Data through May 2026.

What the data says

Mornings have a slight edge.

Departures between 9 AM–12 PM arrived on time 100% of the time, against 94% between 6–9 AM.

Skip Thursday if you can.

DL 4042 arrived on time 100% of the time on Sundays. On Thursdays: 91%.

Better than the ONT–SEA route average.

DL 4042 arrived on time 95% of the time, versus 87% across the ONT–SEA route.

Better than the Delta Air Lines network average.

DL 4042 arrived on time 95% of the time, versus 81% across the Delta Air Lines network.

The breakdown

On-time by weekday
  • Mon94%(52 flights)
  • Tue96%(52 flights)
  • Wed96%(51 flights)
  • Thu91%(53 flights)
  • Fri91%(54 flights)
  • Sat94%(54 flights)
  • Sun100%(55 flights)
On-time by departure window
  • 6–9 AM94%(321 flights)
  • 9 AM–12 PM100%(25 flights)
  • 12–3 PM96%(25 flights)
On-time trend by month
98%
May

Jun 90% → May 98% on time

On-time arrival percentage by month
MonthOn-time percentageFlights
June 202590%30
July 202597%31
August 202594%31
September 202597%29
October 202597%31
November 202597%30
December 202597%30
January 202687%31
February 202696%28
March 202690%31
April 202695%19
May 202698%50
Departures on time
95%
Diverted
0.5%
Flights flown
371
Months covered
12

Same route, other flights

Keep nerding

Based on 373 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.