Connection · one ticket · schedule Jun 6 – Jul 31, 2026 · records Aug 2025 – Jul 2026
Seattle → Boston via San Francisco: arrives on time 45%
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08:45 SEA → 11:03 SFOUA 2831 · United · 2h 18m · 33% on time, 2.8% cancelled
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1h 22m layover in San Francisco (SFO) · 45 min minimum on one ticket
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12:25 SFO → 21:21 BOSUA 1372 · United · 5h 56m · 79% on time, 1.2% cancelled
Total trip 9h 36m, scheduled departure to arrival (Boston is 3 h ahead of Seattle). Times are local. Both flew on 56 of the last 56 days.
Makes the connection59%The first flight arrived more than 37 minutes late on 41% of the days it flew: too late for the 45-minute minimum connection on a 1h 22m layover.
Arrives on time45%First flight not cancelled (2.8% are) × connection made (59%) × second flight not cancelled (1.2% are) and within 15 minutes (79%).
Total trip9h 36mSEA 08:45 to BOS 21:21, layover included
Tight connection: often missed. The first flight is late enough to miss it on more than 1 day in 4.
Not yet counted: the second flight also leaving late (which helps), gate-to-gate distance at the hub, and rebooking after a missed connection.