UAL521 is operated by UNITED AIRLINES INC between George Bush Intercontinental Houston Airport (KIAH) and General Edward Lawrence Logan International Airport (KBOS). The flight is most often flown by a BOEING Boeing 737 MAX 9. Typical block time is 3h 11m. SkyMeter has observed 84 legs of this flight number via ADS-B.

✈
FLIGHTS
84
last 90 days
⏱
AVG DURATION
3h 11m
tracked time
📅
SERVICE PERIOD
5/27/2025 → 9/5/2026
first → last seen
🗺
ROUTES / TYPES
12 / 6
city pairs · airframes
⚠
INCIDENT RATE
0.0%
0 flagged

Routes flown

By count · last 90 days

8
KIAH → KBOS
64
avg 3h 23m · George Bush Intercontinental Houston → General Edward Lawrence Logan
KPWM → KIAH
5
avg 4h 0m · Portland International Jetport → George Bush Intercontinental Houston
84TA → KBOS
1
avg 3h 21m · Allied Northborough Heliport → General Edward Lawrence Logan
KATL → KIAH
1
avg 1h 32m · Hartsfield Jackson Atlanta → George Bush Intercontinental Houston
KIAD → KCLT
1
avg 1h 15m · Washington Dulles → Charlotte Douglas
6XS1 → KBOS
1
avg 3h 23m · Northeast Medical Center Hospital Heliport → General Edward Lawrence Logan
US-0188 → KABQ
1
avg 1h 56m · Coast Guard Air Station San Francisco → Albuquerque International Sunport
62TS → KBOS
1
avg 3h 32m · Gateway Helistop → General Edward Lawrence Logan

Aircraft types

Equipment used on this number

6
B39M BOEING Boeing 737 MAX 9
113
A319 AIRBUS Airbus A319
12
B739 BOEING Boeing 737-900
10
B38M BOEING Boeing 737 MAX 8
3
A320 AIRBUS Airbus A320
1
B737 BOEING Boeing 737-700
1

Safety profile

Flagged flights · last 90 days

Go-arounds
0
Unstable approach
0
Rejected TO
0
Stall warnings
0
Overspeeds
0
Runway excursion
0
Counts represent flights with at least one occurrence of each flag, not the total event count. See /incidents for individual events.

Recent flights

Newest 30 operations of UAL521

30
N37510BOEING Boeing 737 MAX 9
→
9/5/2026
9m
No alerts
Replay Analysis
N27476BOEING Boeing 737 MAX 9
→
9/5/2026
3h 31m
No alerts
Replay Analysis
N27476BOEING Boeing 737 MAX 9
→
9/4/2026
8m
No alerts
Replay Analysis
N27511BOEING Boeing 737 MAX 9
→
9/4/2026
3h 13m
No alerts
Replay Analysis
N17452BOEING Boeing 737 MAX 9
→
9/3/2026
3h 25m
No alerts
Replay Analysis
N75433BOEING Boeing 737-900
→
9/2/2026
3h 35m
No alerts
Replay Analysis
N37545BOEING Boeing 737 MAX 9
→
9/1/2026
3h 14m
No alerts
Replay Analysis
N37545BOEING Boeing 737 MAX 9
→
8/31/2026
3h 27m
No alerts
Replay Analysis
N37545BOEING Boeing 737 MAX 9
→
8/31/2026
12m
No alerts
Replay Analysis
N17455BOEING Boeing 737 MAX 9
→
8/31/2026
3h 15m
No alerts
Replay Analysis
N47357BOEING Boeing 737 MAX 8
→
8/30/2026
3h 11m
No alerts
Replay Analysis
N47357BOEING Boeing 737 MAX 8
→
8/29/2026
3h 19m
No alerts
Replay Analysis
N47357BOEING Boeing 737 MAX 8
→
8/29/2026
7m
No alerts
Replay Analysis
N27526BOEING Boeing 737 MAX 9
→
8/29/2026
3h 13m
No alerts
Replay Analysis
N57466BOEING Boeing 737 MAX 9
→
8/28/2026
3h 42m
No alerts
Replay Analysis
N57466BOEING Boeing 737 MAX 9
→
8/27/2026
3h 5m
No alerts
Replay Analysis
N57466BOEING Boeing 737 MAX 9
→
8/26/2026
3h 16m
No alerts
Replay Analysis
N57466BOEING Boeing 737 MAX 9
→
8/26/2026
10m
No alerts
Replay Analysis
N27568BOEING Boeing 737 MAX 9
→
8/26/2026
3h 21m
No alerts
Replay Analysis
N27568BOEING Boeing 737 MAX 9
→
8/25/2026
11m
No alerts
Replay Analysis
N27568BOEING Boeing 737 MAX 9
→
8/25/2026
3h 33m
No alerts
Replay Analysis
N17460BOEING Boeing 737 MAX 9
→
8/25/2026
3h 27m
No alerts
Replay Analysis
N37561BOEING Boeing 737 MAX 9
→
8/24/2026
3h 13m
No alerts
Replay Analysis
N47434BOEING Boeing 737 MAX 9
→
8/23/2026
3h 15m
No alerts
Replay Analysis
N27419BOEING Boeing 737 MAX 9
→
8/22/2026
3h 20m
No alerts
Replay Analysis
N17406BOEING Boeing 737 MAX 9
→
8/21/2026
3h 15m
No alerts
Replay Analysis
N37551BOEING Boeing 737 MAX 9
→
8/20/2026
3h 21m
No alerts
Replay Analysis
N17403BOEING Boeing 737 MAX 9
→
8/19/2026
3h 2m
No alerts
Replay Analysis
N17403BOEING Boeing 737 MAX 9
→
8/18/2026
3h 12m
No alerts
Replay Analysis
N17403BOEING Boeing 737 MAX 9
→
8/18/2026
10m
No alerts
Replay Analysis
© SkyMeter · All flight data subject to ODbL attribution · Tracked: 90-day window