United Flight 645 Deals & Information (2025/2026)

Wander Wisely with exceptional service, 24/7 supportOpens in a new window

Feel at ease with free flight cancellations within 24 hours of booking

Change your flight without a fee on select flights

United Flight 645 Route Deals From $129

The cheapest prices found with in the last 7 days for return flights were $189 and $129 for one-way flights to Sioux Falls Regional for the period specified. Prices and availability are subject to change. Additional terms apply.

Fri, Jul 4 - Mon, Jul 7
DEN
Denver Intl.
FSD
Sioux Falls Regional
$189 Roundtrip, found 2 days ago
$189
Roundtrip
found 2 days ago
Select United flight, departing Fri, Jul 4 from Denver Intl. to Sioux Falls Regional, returning Mon, Jul 7, priced at $189 found 2 days ago
Fri, May 23 - Sun, May 25
DEN
Denver Intl.
FSD
Sioux Falls Regional
$193 Roundtrip, found 6 hours ago
$193
Roundtrip
found 6 hours ago
Select United flight, departing Fri, May 23 from Denver Intl. to Sioux Falls Regional, returning Sun, May 25, priced at $193 found 6 hours ago
Fri, May 9 - Sun, May 11
DEN
Denver Intl.
FSD
Sioux Falls Regional
$201 Roundtrip, found 2 days ago
$201
Roundtrip
found 2 days ago
Select United flight, departing Fri, May 9 from Denver Intl. to Sioux Falls Regional, returning Sun, May 11, priced at $201 found 2 days ago
Fri, Jul 4 - Mon, Jul 7
DEN
Denver Intl.
FSD
Sioux Falls Regional
$219 Roundtrip, found 2 days ago
$219
Roundtrip
found 2 days ago
Select United flight, departing Fri, Jul 4 from Denver Intl. to Sioux Falls Regional, returning Mon, Jul 7, priced at $219 found 2 days ago
Fri, May 23 - Sun, May 25
DEN
Denver Intl.
FSD
Sioux Falls Regional
$223 Roundtrip, found 6 hours ago
$223
Roundtrip
found 6 hours ago
Select United flight, departing Fri, May 23 from Denver Intl. to Sioux Falls Regional, returning Sun, May 25, priced at $223 found 6 hours ago
Fri, May 9 - Sun, May 11
DEN
Denver Intl.
FSD
Sioux Falls Regional
$227 Roundtrip, found 2 days ago
$227
Roundtrip
found 2 days ago
Select United flight, departing Fri, May 9 from Denver Intl. to Sioux Falls Regional, returning Sun, May 11, priced at $227 found 2 days ago
Sat, May 17 - Tue, May 20
DEN
Denver Intl.
FSD
Sioux Falls Regional
$229 Roundtrip, found 14 hours ago
$229
Roundtrip
found 14 hours ago
Select United flight, departing Sat, May 17 from Denver Intl. to Sioux Falls Regional, returning Tue, May 20, priced at $229 found 14 hours ago
Thu, Jul 3 - Mon, Jul 7
DEN
Denver Intl.
FSD
Sioux Falls Regional
$231 Roundtrip, found 2 days ago
$231
Roundtrip
found 2 days ago
Select United flight, departing Thu, Jul 3 from Denver Intl. to Sioux Falls Regional, returning Mon, Jul 7, priced at $231 found 2 days ago
Fri, Jun 6 - Sun, Jun 8
DEN
Denver Intl.
FSD
Sioux Falls Regional
$235 Roundtrip, found 4 hours ago
$235
Roundtrip
found 4 hours ago
Select United flight, departing Fri, Jun 6 from Denver Intl. to Sioux Falls Regional, returning Sun, Jun 8, priced at $235 found 4 hours ago
Sun, May 25 - Thu, May 29
DEN
Denver Intl.
FSD
Sioux Falls Regional
$239 Roundtrip, found 2 days ago
$239
Roundtrip
found 2 days ago
Select United flight, departing Sun, May 25 from Denver Intl. to Sioux Falls Regional, returning Thu, May 29, priced at $239 found 2 days ago

Frequently asked questions

What route does flight number UA645 take?
UA645 serves multiple routes, but the most common is between FCA and DIA airport. If your flight goes direct, you’ll land in around 2 hours and 6 minutes. Multi-stop flights can also use this number, as can services on other routes.
What kind of plane is on flight number UA645?
UA645 is a flight number that is used on many routes. If you’ve booked a ticket on the most popular one, Glacier Park Intl. Airport (FCA) to Denver Intl. Airport (DEN), chances are you’ll be hopping aboard the Boeing 737-800.
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 UA645 flight with Travelocity, please visit our Customer Service Portal.