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ATIS Alerts Smart Flight Search

Find the flight least likely to be delayed

Beta

We rank real flight numbers by how often they flew and arrived on time over the last 12 months, adjusted for your travel month and departure time, then check nearby airports and calmer connections. US airlines and airports.

ONT → MDW

Ontario to Chicago: 360 nonstop flights a year

On time (12 months)

90%

Cancelled

0.3%

avg delay 5 min

Best time to leave

No clear winner

Most reliable airline

Southwest

90% chance on time

Check ONT to MDW fares

Lowest nonstop fare seen in the next two months: $150 (Southwest 3270 on 2026-10-26). Fares open on our travel partner (Aviasales). Pick the flight number you chose here.

Most reliable nonstop flights

Ranked by the chance the flight operates and arrives within 15 minutes of schedule, from Jun 2025 to May 2026 records.

  1. #1 · Southwest 3658

    11:55 PM → 5:40 AM3h 45m nonstop

    Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Southwest 4134; its record covers all of them.

    90%

    chance on time

    On time (history)
    91%
    Cancelled
    0.0%
    Avg arrival delay
    5 min
    • Arrived on time 91% of the time (86 flights, Jun 2025 to May 2026).
    • Never cancelled in 87 scheduled flights.

    Moderate track record · 86 flights

    Find Southwest 3658 fares Opens this date on Aviasales

Airlines on this route

Season-adjusted chance of operating and arriving on time.

  • Southwest Airlines90%

    360 flights · 90% on time as flown · 0.3% cancel

On time by departure time

All airlines, scheduled local departure, Jun 2025 to May 2026.

  • Before 9 AM91%

    227 flights · avg delay 5 min

  • 9 AM to noon89%

    37 flights · avg delay 6 min

  • After 9 PM91%

    88 flights · avg delay 5 min

Best day: Friday (92%). Worst: Wednesday (87%).

Historical odds, not a guarantee. Built from the US DOT Bureau of Transportation Statistics on-time reports (Jun 2025 to May 2026), FAA ground stop and delay program advisories, and 20 years of airport weather observations. Covers US airlines that report to the DOT; schedules are flights operated recently, so confirm times when you book. ATIS Alerts is not affiliated with any airline. Fares are what Aviasales travelers saw in recent searches (USD, one way, 1 adult), not live quotes; the partner site shows the current price. Fare links go to our travel partner and may earn us a commission at no cost to you. Affiliate disclosure