United Flight 643 Deals & Information (2025/2026)

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United Flight 643 Route Deals From $71

The cheapest prices found with in the last 7 days for return flights were $110 and $71 for one-way flights to San Francisco Intl. for the period specified. Prices and availability are subject to change. Additional terms apply.

Sat, Feb 28 - Sun, Mar 1
SEA
Seattle - Tacoma Intl.
SFO
San Francisco Intl.
$110 Roundtrip, found 6 days ago
$110
Roundtrip
found 6 days ago
Select United flight, departing Sat, Feb 28 from Seattle - Tacoma Intl. to San Francisco Intl., returning Sun, Mar 1, priced at $110 found 6 days ago
Sat, Feb 28 - Sun, Mar 1
SEA
Seattle - Tacoma Intl.
SFO
San Francisco Intl.
$111 Roundtrip, found 6 days ago
$111
Roundtrip
found 6 days ago
Select United flight, departing Sat, Feb 28 from Seattle - Tacoma Intl. to San Francisco Intl., returning Sun, Mar 1, priced at $111 found 6 days ago
Sat, Jan 17 - Tue, Jan 20
SEA
Seattle - Tacoma Intl.
SFO
San Francisco Intl.
$116 Roundtrip, found 4 days ago
$116
Roundtrip
found 4 days ago
Select United flight, departing Sat, Jan 17 from Seattle - Tacoma Intl. to San Francisco Intl., returning Tue, Jan 20, priced at $116 found 4 days ago
Mon, Jan 26 - Fri, Jan 30
SEA
Seattle - Tacoma Intl.
SFO
San Francisco Intl.
$120 Roundtrip, found 21 hours ago
$120
Roundtrip
found 21 hours ago
Select United flight, departing Mon, Jan 26 from Seattle - Tacoma Intl. to San Francisco Intl., returning Fri, Jan 30, priced at $120 found 21 hours ago
Sat, Jan 17 - Tue, Jan 20
SEA
Seattle - Tacoma Intl.
SFO
San Francisco Intl.
$128 Roundtrip, found 4 days ago
$128
Roundtrip
found 4 days ago
Select United flight, departing Sat, Jan 17 from Seattle - Tacoma Intl. to San Francisco Intl., returning Tue, Jan 20, priced at $128 found 4 days ago

Frequently asked questions

What route does flight number UA643 take?
UA643 takes approximately 5 hours and 3 minutes to jet directly from Kona Intl. Airport (KOA) to San Francisco, CA Airport (SFO-San Francisco Intl.). Sure, there's magic in the destination, but getting there is half the fun!
How often is UA643 on time?
United Airlines flight number UA643 from Kailua-Kona, HI Airport (KOA-Kona Intl.) to SFO runs on time 100% of the time — so you can relax knowing that you'll reach your destination ASAP. If this service happens to be late, you'll probably wait roughly 6 minutes. This route has a 4.55-star rating.
What kind of plane is on flight number UA643?
The route for UA643 is most commonly KOA to SFO, and the Boeing 737-900 is the type of plane you're likely to be heading off on.
If I am not able to travel due to COVID-19, can I change my flight to a later date?
For more info about changing your UA643 flight with Travelocity, please visit our Customer Service Portal.