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United Airlines / BOS → IAD

UA 1734 on time

United Airlines 1734: Boston to Washington at 5:45 a.m.; Washington to Los Angeles at 8:15 a.m. (past 12 months). Figures below the title are for BOS → IAD, its busiest leg

On time
94%
345 flights · likely 91–96%
Cancelled
2.3%
of scheduled flights
Typical arrival
−13 min
median vs schedule
When late
+49 min
average delay
Similar flights
94%
UA, same route & hour

About 1 in 16 UA 1734 flights from Boston arrived 15+ minutes late, diverted or cancelled over the past year (6%); 2.3% were cancelled. The typical flight landed 13 minutes early.

UA 1734: BOS → IAD

Scheduled to leave Boston at 5:45 a.m. local time. Over the past year it arrived on time 94% of the time (345 flights), in line with other UA flights on the route at that hour (94%). Last seen in the data Aug 31, 2026.

Month by month

40%70%100%Sep 2025: 100% on time (30 flights)100SepOct 2025: 94% on time (31 flights)94OctNov 2025: 100% on time (30 flights)100NovDec 2025: 94% on time (31 flights)94DecJan 2026: 79% on time (19 flights)79JanFeb 2026: 78% on time (23 flights)78FebMar 2026: 96% on time (28 flights)96MarApr 2026: 100% on time (30 flights)100AprMay 2026: 97% on time (31 flights)97MayJun 2026: 97% on time (30 flights)97JunJul 2026: 90% on time (31 flights)90JulAug 2026: 94% on time (31 flights)94Aug

By day of week

DayFlightsOn time
Monday5391%
Tuesday4498%
Wednesday4691%
Thursday5296%
Friday5298%
Saturday4789%
Sunday5194%

Why it was late

Airline (crew, maintenance, ops) 74%Air traffic & airport (NAS) 21%Severe weather 5%

All flights BOS → IAD · Connecting off UA 1734? Check the risk

UA 1734: IAD → LAX

Scheduled to leave Washington at 8:15 a.m. local time. Over the past year it arrived on time 85% of the time (203 flights), in line with other UA flights on the route at that hour (87%). Last seen in the data Aug 31, 2026.

Month by month

40%70%100%May 2025: too few flights (10 flights)MayDec 2025: too few flights (14 flights)DecJan 2026: 71% on time (31 flights)71JanFeb 2026: 85% on time (27 flights)85FebMar 2026: 81% on time (31 flights)81MarApr 2026: 87% on time (30 flights)87AprMay 2026: 96% on time (25 flights)96MayJun 2026: too few flights (13 flights)JunJul 2026: too few flights (13 flights)JulAug 2026: 95% on time (19 flights)95Aug

By day of week

DayFlightsOn time
Monday3797%
Tuesday2282%
Wednesday2195%
Thursday3781%
Friday3686%
Saturday2580%
Sunday2572%

Why it was late

Late inbound plane 41%Airline (crew, maintenance, ops) 37%Air traffic & airport (NAS) 15%Severe weather 7%

All flights IAD → LAX · Connecting off UA 1734? Check the risk

Questions

How often is UA 1734 from BOS to IAD late?

United Airlines 1734 from Boston, MA to Washington, DC arrived 15 or more minutes late, was diverted or was cancelled on 6% of 345 scheduled flights between September 2025 and August 2026. 2.3% were cancelled.

How often is UA 1734 from IAD to LAX late?

United Airlines 1734 from Washington, DC to Los Angeles, CA arrived 15 or more minutes late, was diverted or was cancelled on 15% of 203 scheduled flights between September 2025 and August 2026. 1.5% 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.