(UNITED STATES) United Airlines ordered FAA-backed ground stops at several hubs after a sudden technology issue on Wednesday evening, August 6, 2025, delaying more than 1,000 flights nationwide. Operations resumed that night, but ripple delays continued into Thursday.
By August 11, the carrier and federal officials said the disruption was resolved, with recovery complete and regular schedules back on track.
What happened and where
United reported a “technology issue” shortly after 6 p.m. ET on August 6. The airline asked the Federal Aviation Administration to hold United mainline departures at key hubs, including Newark (EWR), San Francisco (SFO), Chicago O’Hare (ORD), Denver (DEN), and Houston (IAH).
Flights already in the air continued to their destinations. Notably, United Express flights were not subject to the ground stops, which applied only to United mainline departures.
United told reporters an internal system called Unimatic — which houses flight information and feeds other operational tools — was disrupted. The outage affected systems tied to weight-and-balance calculations and flight time tracking, so the airline paused departures to preserve safety margins until systems stabilized.
Latest status and numbers
- On August 6, more than 1,000 United flights were delayed and more than 40 were canceled, according to FlightAware figures cited by national outlets.
- Roughly 35% of United’s flights were delayed and about 7% canceled that day.
- By late morning on August 7 (Chicago time), 9% of United flights were delayed and 5% canceled, with 42 cancellations at ORD (41 on United), as the airline pushed through the backlog.
United said “the underlying technology issue has been resolved,” but warned of residual delays during recovery. The FAA confirmed it supported United’s recovery efforts and remained in close contact.
What officials and United said
- United apologized and described the incident as a technology disruption affecting weight-and-balance and related tools. The airline said it was “working with customers to get them to their destinations.”
- United treated the event as controllable delays for purposes of expense coverage and confirmed to ABC News that this was not a cyberattack.
- U.S. Transportation Secretary Sean Duffy said the problem was specific to United and unrelated to the broader national air traffic control system.
- The FAA said it was aware of United’s issue, provided support, and did not restrict the National Airspace System beyond United’s requested airport-specific ground stops.
Why this matters for travelers
Large airline IT outages trigger chain reactions: aircraft and crews get out of position, gates clog, and connections break down. In this incident, the airline’s flight information tool (Unimatic) and the weight-and-balance computer system were central to the disruption. When those systems fail, departures are paused until safe operations can resume.
For travelers with time-sensitive plans — school start dates, medical travel, or family events — every hour can matter. Analysis by VisaVerge.com shows day-of-airline technology problems often hit the biggest hubs hardest, which is what happened at ORD, EWR, DEN, IAH, and SFO, where the largest ripple effects occurred.
If you were affected: what you can do now
- Keep your receipts. United said it would cover meals and hotels where applicable because it treated the event as a controllable delay. Save proof of payment and submit reimbursement requests via the United app or united.com.
- Check your flight status often. Statuses changed quickly as the airline cleared the backlog. Use the United app or website for gate changes, delay notices, or proactive rebooking offers.
- Know your flight type. The ground stops applied to United mainline departures, not United Express. Check your carrier code — UA (mainline) versus a partner code for Express — to understand possible impact.
- Plan extra time at hubs. If your trip routed through ORD, EWR, DEN, IAH, or SFO, expect longer lines, slower baggage delivery, and tighter connections during recovery.
- Track your bag. United’s app supports bag tracking after arrival, useful if bags arrive late while schedules normalize.
For official air traffic advisories used during airline-requested ground stops, see the FAA Command Center Advisories page: https://www.fly.faa.gov/adv/advAdvisories.jsp.
The recovery timeline
- Shortly after 6 p.m. ET, Aug 6 — United identifies the technology issue and requests FAA ground stops at multiple hubs. Flights already airborne continue.
- Late evening, Aug 6 — United announces the core problem is fixed. Delays and cancellations persist as crews and aircraft are repositioned.
- Aug 7 (morning to midday, local time) — Disruptions continue but ease. FAA supports United as the backlog is cleared. ORD records a cluster of cancellations.
- Aug 7–8 — United’s travel alert flags possible impacts across many U.S. airports and some European gateways (LHR, FRA, MUC). Conditions improve as operations normalize.
Customer care and coverage
United labeled the event controllable and said it would provide hotels and meals where policies apply. The airline asked customers to use digital channels for rebooking and expense claims and issued public apologies on social media.
What didn’t happen
Officials emphasized the disruption was not caused by federal systems or malicious activity:
- Not a cyberattack — United confirmed this.
- Not an ATC failure — DOT said the problem was specific to United’s systems, not national air traffic control.
- FAA involvement limited to support — The FAA provided assistance but did not impose a nationwide system limit.
Policy and operations lessons
- System reliability: The Unimatic disruption highlights how interdependent airline tools are. A failure in a key system can stall weight-and-balance, flight time tracking, and other essential operations, underscoring the need for strong backups and fast failover.
- Accountability & customer protections: By treating delays as controllable, United aligned with expectations that airlines assist customers during airline-caused disruptions. Exact reimbursement follows the carrier’s contract of carriage.
- ATC independence: DOT’s statement clarified the line between airline IT problems and federal air traffic control — responsibility and fixes rest primarily with the airline.
- Industry context: United’s policy materials emphasize investments in technology and system reliability, including support for ATC modernization under the 2024 FAA reauthorization. Staffing and modernization remain priorities, even though this event was not ATC-related.
Recent United policy changes that may affect you
- Check-in cutoff (since June 3, 2025): United’s domestic check-in cutoff for customers without checked bags moved from 30 to 45 minutes before departure. This matters on recovery days if you’re rebooked and racing the clock.
- MileagePlus 2025 updates: United previewed higher qualification thresholds for 2025 (for 2026 status) and a mid-2025 change to allow PlusPoints to be used in new ways (PQPs/PQFs, TravelBank, bonus miles, or gifting status). Details and timing are to be released in 2025.
Key takeaways
- Cause: Technology issue affecting Unimatic and weight-and-balance tools.
- Response: FAA ground stops at major hubs at United’s request.
- Impact: 1,000+ delays, dozens of cancellations on Aug 6; residual issues on Aug 7.
- Security: United said it was not a cyberattack.
- Customer care: United treated disruptions as controllable and offered hotels and meals where applicable.
- What to do now: Use the United app for rebooking, keep receipts for reimbursement, and plan extra time at major hubs during recovery.
This Article in a Nutshell
On August 6, 2025 United’s Unimatic outage triggered FAA-backed ground stops at major hubs, delaying over 1,000 flights. The airline paused mainline departures while weight-and-balance and timing systems recovered. United offered hotels and meals for controllable delays, urged app use for rebooking, and reported full recovery by August 11.
