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United Airlines / ORD → SFO

UA 543 on time

United Airlines 543: Chicago to San Francisco at 10:30 a.m.; Buffalo to Chicago at 7:00 a.m. (past 12 months). Figures below the title are for ORD → SFO, its busiest leg

On time
57%
180 flights · likely 50–64%
Cancelled
1.7%
of scheduled flights
Typical arrival
+10 min
median vs schedule
When late
+83 min
average delay
Similar flights
58%
UA, same route & hour

About 1 in 2 UA 543 flights from Chicago arrived 15+ minutes late, diverted or cancelled over the past year (43%); 1.7% were cancelled. The typical flight landed 10 minutes late.

UA 543: ORD → SFO

Scheduled to leave Chicago at 10:30 a.m. local time. Over the past year it arrived on time 57% of the time (180 flights), in line with other UA flights on the route at that hour (58%). Last seen in the data Aug 31, 2026.

Month by month

40%70%100%Mar 2026: 85% on time (27 flights)85MarApr 2026: 57% on time (30 flights)57AprMay 2026: 52% on time (31 flights)52MayJun 2026: 60% on time (30 flights)60JunJul 2026: 45% on time (31 flights)45JulAug 2026: 48% on time (31 flights)48Aug

By day of week

DayFlightsOn time
Monday2635%
Tuesday2572%
Wednesday2544%
Thursday2662%
Friday2646%
Saturday2669%
Sunday2673%

Why it was late

Late inbound plane 40%Air traffic & airport (NAS) 37%Airline (crew, maintenance, ops) 22%Severe weather 1%

All flights ORD → SFO · Connecting off UA 543? Check the risk

UA 543: BUF → ORD

Scheduled to leave Buffalo at 7:00 a.m. local time. Over the past year it arrived on time 82% of the time (161 flights), in line with other UA flights on the route at that hour (82%). Last seen in the data Aug 31, 2026.

Month by month

40%70%100%Feb 2026: 71% on time (17 flights)71FebMar 2026: 77% on time (31 flights)77MarApr 2026: 73% on time (30 flights)73AprMay 2026: 90% on time (31 flights)90MayJun 2026: 90% on time (30 flights)90JunJul 2026: too few flights (2 flights)JulAug 2026: 85% on time (20 flights)85Aug

By day of week

DayFlightsOn time
Monday2383%
Tuesday2286%
Wednesday2383%
Thursday2383%
Friday2370%
Saturday2387%
Sunday2483%

Why it was late

Air traffic & airport (NAS) 48%Airline (crew, maintenance, ops) 44%Late inbound plane 8%

All flights BUF → ORD · Connecting off UA 543? Check the risk

Questions

How often is UA 543 from ORD to SFO late?

United Airlines 543 from Chicago, IL to San Francisco, CA arrived 15 or more minutes late, was diverted or was cancelled on 43% of 180 scheduled flights between September 2025 and August 2026. 1.7% were cancelled.

How often is UA 543 from BUF to ORD late?

United Airlines 543 from Buffalo, NY to Chicago, IL arrived 15 or more minutes late, was diverted or was cancelled on 18% of 161 scheduled flights between September 2025 and August 2026. 2.5% were cancelled.

Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check United Airlines for today's flight. Method.