United Airlines flight UA 521: Multiple routes

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Select flight date:
FLIGHT SCHEDULE
Direct Flights:
Daily 15:45 Atlanta (ATL) N 17:00 Houston George Bush (IAH) C
UA 521 Non-stop Airbus A319 (319) 2:15 Effective 2026-03-29 through 2026-04-29
Daily 15:45 Atlanta (ATL) N 17:00 Houston George Bush (IAH) C
UA 521 Non-stop Boeing 737-700 (73G) 2:15 Effective 2026-04-30 through 2026-05-20
Daily 15:45 Atlanta (ATL) N 17:00 Houston George Bush (IAH) C
UA 521 Non-stop Airbus A319 (319) 2:15 Effective from 2026-05-21
Thu,Fri 15:57 Atlanta (ATL) N 17:25 Houston George Bush (IAH) C
UA 521 Non-stop Airbus A320 (320) 2:28 Effective 2026-03-05 through 2026-03-27
Sat 15:57 Atlanta (ATL) N 17:25 Houston George Bush (IAH) C
UA 521 Non-stop Boeing 737-700 (73G) 2:28 Effective 2026-03-07 through 2026-03-28
Mon-Wed,Sun 15:57 Atlanta (ATL) N 17:25 Houston George Bush (IAH) C
UA 521 Non-stop Airbus A319 (319) 2:28 Effective 2026-03-08 through 2026-03-25
Daily 16:02 Atlanta (ATL) N 17:32 Houston George Bush (IAH) C
UA 521 Non-stop Boeing 737-800 (738) 2:30 Effective 2026-02-12 through 2026-03-04
Sat 16:42 Saint Louis (STL) 1 19:10 Houston George Bush (IAH) C
UA 521 Non-stop Airbus A320 (320) 2:28 Effective 2026-01-10 through 2026-02-07
Mon,Wed-Fri 18:17 Boston Logan (BOS) B 19:48 Newark Liberty, New York (EWR) C
UA 521 Non-stop Boeing 737-700 (73G) 1:31 Effective 2026-01-07 through 2026-02-11
Sun 18:25 Boston Logan (BOS) B 19:56 Newark Liberty, New York (EWR) C
UA 521 Non-stop Boeing 737-700 (73G) 1:31 Effective 2026-01-11 through 2026-02-08
Tue 18:29 Boston Logan (BOS) B 19:59 Newark Liberty, New York (EWR) C
UA 521 Non-stop Boeing 737-700 (73G) 1:30 Effective 2026-01-06 through 2026-02-10
Daily 18:35 Houston George Bush (IAH) C 23:32 Boston Logan (BOS) B
UA 521 Non-stop Boeing 737-900 (739) 3:57 Effective 2026-03-29 through 2026-04-29
Daily 18:35 Houston George Bush (IAH) C 23:20 Boston Logan (BOS) B
UA 521 Non-stop Boeing 737 MAX 8 (7M8) 3:45 Effective 2026-04-30 through 2026-05-20
Daily 18:35 Houston George Bush (IAH) C 23:20 Boston Logan (BOS) B
UA 521 Non-stop Boeing 737-800 (738) 3:45 Effective from 2026-05-21
Mon,Wed-Fri,Sun 18:42 Houston George Bush (IAH) C 23:30 Boston Logan (BOS) B
UA 521 Non-stop Boeing 737 MAX 8 (7M8) 3:48 Effective 2026-03-05 through 2026-03-27
Sat 18:42 Houston George Bush (IAH) C 23:30 Boston Logan (BOS) B
UA 521 Non-stop Boeing 737-800 (738) 3:48 Effective 2026-03-07 through 2026-03-28
Mon-Fri 18:43 Houston George Bush (IAH) C 23:12 New York LaGuardia (LGA) B
UA 521 Non-stop Boeing 737-800 (738) 3:29 Effective 2026-02-12 through 2026-03-04
Mon-Fri,Sun 19:15 Newark Liberty, New York (EWR) A 22:32 Fort Lauderdale (FLL) 1
UA 521 Non-stop Boeing 737 MAX 8 (7M8) 3:17 Valid until 2026-01-04
Mon 19:15 Newark Liberty, New York (EWR) A 22:32 Fort Lauderdale (FLL) 1
UA 521 Non-stop Boeing 737-900 (739) 3:17 Operates only on 2026-01-05
Sat 19:22 Newark Liberty, New York (EWR) A 22:39 Fort Lauderdale (FLL) 1
UA 521 Non-stop Boeing 737-900 (739) 3:17 Valid until 2026-01-03
Non-Direct Flights:
Daily 15:45 Atlanta (ATL) N 23:32 Boston Logan (BOS) B
UA 521 1-stop Airbus A319 (319) 7:47 Effective 2026-03-29 through 2026-04-29
Daily 15:45 Atlanta (ATL) N 23:20 Boston Logan (BOS) B
UA 521 1-stop Boeing 737-700 (73G) 7:35 Effective 2026-04-30 through 2026-05-20
Daily 15:45 Atlanta (ATL) N 23:20 Boston Logan (BOS) B
UA 521 1-stop Airbus A319 (319) 7:35 Effective from 2026-05-21
Thu,Fri 15:57 Atlanta (ATL) N 23:30 Boston Logan (BOS) B
UA 521 1-stop Airbus A320 (320) 7:33 Effective 2026-03-05 through 2026-03-27
Sat 15:57 Atlanta (ATL) N 23:30 Boston Logan (BOS) B
UA 521 1-stop Boeing 737-700 (73G) 7:33 Effective 2026-03-07 through 2026-03-28
Mon,Wed,Sun 15:57 Atlanta (ATL) N 23:30 Boston Logan (BOS) B
UA 521 1-stop Airbus A319 (319) 7:33 Effective 2026-03-08 through 2026-03-25
Mon-Fri 16:02 Atlanta (ATL) N 23:12 New York LaGuardia (LGA) B
UA 521 1-stop Boeing 737-800 (738) 7:10 Effective 2026-02-12 through 2026-03-04
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This flight number is listed as serving the following routes:


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United Airlines flight UA 521: Multiple routes
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Select flight date:
FLIGHT SCHEDULE
Direct Flights:
United Airlines UA521
15:45
Atlanta (ATL) N

17:00
Houston George Bush (IAH) C
Effective 2026-03-29 through 2026-04-29
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 2:15, non-stop
Airbus A319 (319)
Direct Flights:
United Airlines UA521
15:45
Atlanta (ATL) N

17:00
Houston George Bush (IAH) C
Effective 2026-04-30 through 2026-05-20
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 2:15, non-stop
Boeing 737-700 (73G)
Direct Flights:
United Airlines UA521
15:45
Atlanta (ATL) N

17:00
Houston George Bush (IAH) C
Effective from 2026-05-21
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 2:15, non-stop
Airbus A319 (319)
Direct Flights:
United Airlines UA521
15:57
Atlanta (ATL) N

17:25
Houston George Bush (IAH) C
Effective 2026-03-05 through 2026-03-27
Mon
-
Tue
-
Wed
-
Thu
Fri
Sat
-
Sun
-
Duration: 2:28, non-stop
Airbus A320 (320)
Direct Flights:
United Airlines UA521
15:57
Atlanta (ATL) N

17:25
Houston George Bush (IAH) C
Effective 2026-03-07 through 2026-03-28
Mon
-
Tue
-
Wed
-
Thu
-
Fri
-
Sat
Sun
-
Duration: 2:28, non-stop
Boeing 737-700 (73G)
Direct Flights:
United Airlines UA521
15:57
Atlanta (ATL) N

17:25
Houston George Bush (IAH) C
Effective 2026-03-08 through 2026-03-25
Mon
Tue
Wed
Thu
-
Fri
-
Sat
-
Sun
Duration: 2:28, non-stop
Airbus A319 (319)
Direct Flights:
United Airlines UA521
16:02
Atlanta (ATL) N

17:32
Houston George Bush (IAH) C
Effective 2026-02-12 through 2026-03-04
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 2:30, non-stop
Boeing 737-800 (738)
Direct Flights:
United Airlines UA521
16:42
Saint Louis (STL) 1

19:10
Houston George Bush (IAH) C
Effective 2026-01-10 through 2026-02-07
Mon
-
Tue
-
Wed
-
Thu
-
Fri
-
Sat
Sun
-
Duration: 2:28, non-stop
Airbus A320 (320)
Direct Flights:
United Airlines UA521
18:17
Boston Logan (BOS) B

19:48
Newark Liberty, New York (EWR) C
Effective 2026-01-07 through 2026-02-11
Mon
Tue
-
Wed
Thu
Fri
Sat
-
Sun
-
Duration: 1:31, non-stop
Boeing 737-700 (73G)
Direct Flights:
United Airlines UA521
18:25
Boston Logan (BOS) B

19:56
Newark Liberty, New York (EWR) C
Effective 2026-01-11 through 2026-02-08
Mon
-
Tue
-
Wed
-
Thu
-
Fri
-
Sat
-
Sun
Duration: 1:31, non-stop
Boeing 737-700 (73G)
Direct Flights:
United Airlines UA521
18:29
Boston Logan (BOS) B

19:59
Newark Liberty, New York (EWR) C
Effective 2026-01-06 through 2026-02-10
Mon
-
Tue
Wed
-
Thu
-
Fri
-
Sat
-
Sun
-
Duration: 1:30, non-stop
Boeing 737-700 (73G)
Direct Flights:
United Airlines UA521
18:35
Houston George Bush (IAH) C

23:32
Boston Logan (BOS) B
Effective 2026-03-29 through 2026-04-29
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 3:57, non-stop
Boeing 737-900 (739)
Direct Flights:
United Airlines UA521
18:35
Houston George Bush (IAH) C

23:20
Boston Logan (BOS) B
Effective 2026-04-30 through 2026-05-20
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 3:45, non-stop
Boeing 737 MAX 8 (7M8)
Direct Flights:
United Airlines UA521
18:35
Houston George Bush (IAH) C

23:20
Boston Logan (BOS) B
Effective from 2026-05-21
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 3:45, non-stop
Boeing 737-800 (738)
Direct Flights:
United Airlines UA521
18:42
Houston George Bush (IAH) C

23:30
Boston Logan (BOS) B
Effective 2026-03-05 through 2026-03-27
Mon
Tue
-
Wed
Thu
Fri
Sat
-
Sun
Duration: 3:48, non-stop
Boeing 737 MAX 8 (7M8)
Direct Flights:
United Airlines UA521
18:42
Houston George Bush (IAH) C

23:30
Boston Logan (BOS) B
Effective 2026-03-07 through 2026-03-28
Mon
-
Tue
-
Wed
-
Thu
-
Fri
-
Sat
Sun
-
Duration: 3:48, non-stop
Boeing 737-800 (738)
Direct Flights:
United Airlines UA521
18:43
Houston George Bush (IAH) C

23:12
New York LaGuardia (LGA) B
Effective 2026-02-12 through 2026-03-04
Mon
Tue
Wed
Thu
Fri
Sat
-
Sun
-
Duration: 3:29, non-stop
Boeing 737-800 (738)
Direct Flights:
United Airlines UA521
19:15
Newark Liberty, New York (EWR) A

22:32
Fort Lauderdale (FLL) 1
Valid until 2026-01-04
Mon
Tue
Wed
Thu
Fri
Sat
-
Sun
Duration: 3:17, non-stop
Boeing 737 MAX 8 (7M8)
Direct Flights:
United Airlines UA521
19:15
Newark Liberty, New York (EWR) A

22:32
Fort Lauderdale (FLL) 1
Operates only on 2026-01-05
Mon
Tue
-
Wed
-
Thu
-
Fri
-
Sat
-
Sun
-
Duration: 3:17, non-stop
Boeing 737-900 (739)
Direct Flights:
United Airlines UA521
19:22
Newark Liberty, New York (EWR) A

22:39
Fort Lauderdale (FLL) 1
Valid until 2026-01-03
Mon
-
Tue
-
Wed
-
Thu
-
Fri
-
Sat
Sun
-
Duration: 3:17, non-stop
Boeing 737-900 (739)
Non-Direct Flights:
United Airlines UA521
15:45
Atlanta (ATL) N

23:32
Boston Logan (BOS) B
Effective 2026-03-29 through 2026-04-29
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 7:47, 1-stop
Airbus A319 (319)
Non-Direct Flights:
United Airlines UA521
15:45
Atlanta (ATL) N

23:20
Boston Logan (BOS) B
Effective 2026-04-30 through 2026-05-20
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 7:35, 1-stop
Boeing 737-700 (73G)
Non-Direct Flights:
United Airlines UA521
15:45
Atlanta (ATL) N

23:20
Boston Logan (BOS) B
Effective from 2026-05-21
Mon
Tue
Wed
Thu
Fri
Sat
Sun
Duration: 7:35, 1-stop
Airbus A319 (319)
Non-Direct Flights:
United Airlines UA521
15:57
Atlanta (ATL) N

23:30
Boston Logan (BOS) B
Effective 2026-03-05 through 2026-03-27
Mon
-
Tue
-
Wed
-
Thu
Fri
Sat
-
Sun
-
Duration: 7:33, 1-stop
Airbus A320 (320)
Non-Direct Flights:
United Airlines UA521
15:57
Atlanta (ATL) N

23:30
Boston Logan (BOS) B
Effective 2026-03-07 through 2026-03-28
Mon
-
Tue
-
Wed
-
Thu
-
Fri
-
Sat
Sun
-
Duration: 7:33, 1-stop
Boeing 737-700 (73G)
Non-Direct Flights:
United Airlines UA521
15:57
Atlanta (ATL) N

23:30
Boston Logan (BOS) B
Effective 2026-03-08 through 2026-03-25
Mon
Tue
-
Wed
Thu
-
Fri
-
Sat
-
Sun
Duration: 7:33, 1-stop
Airbus A319 (319)
Non-Direct Flights:
United Airlines UA521
16:02
Atlanta (ATL) N

23:12
New York LaGuardia (LGA) B
Effective 2026-02-12 through 2026-03-04
Mon
Tue
Wed
Thu
Fri
Sat
-
Sun
-
Duration: 7:10, 1-stop
Boeing 737-800 (738)
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This flight number is listed as serving the following routes:
  • Atlanta (ATL) - Boston Logan (BOS)
  • Atlanta (ATL) - Houston George Bush (IAH)
  • Atlanta (ATL) - New York LaGuardia (LGA)
  • Boston Logan (BOS) - Newark Liberty, New York (EWR)
  • Houston George Bush (IAH) - Boston Logan (BOS)
  • Houston George Bush (IAH) - New York LaGuardia (LGA)
  • Newark Liberty, New York (EWR) - Fort Lauderdale (FLL)
  • Saint Louis (STL) - Houston George Bush (IAH)
All United Airlines flights
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