Flights at two of the United States’ busiest hubs, Chicago O’Hare International Airport and Miami International Airport, faced fresh disruption today after the Federal Aviation Administration (FAA) ordered ground stops that rippled across the networks of American Airlines and United Airlines. While both stoppages were relatively brief, the combination of weather, lingering system strain and tight winter schedules left thousands of passengers dealing with delays, missed connections and lingering uncertainty over the stability of U.S. air travel in early 2026.

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What Happened at Chicago O’Hare

Chicago O’Hare, a primary hub for both United Airlines and American Airlines, has endured repeated bouts of disruption in recent months, ranging from harsh winter weather to broader FAA capacity cuts tied to the ongoing federal government shutdown. The latest interruptions today followed a series of operational slowdowns and recent ground stops that underscored just how vulnerable the complex hub remains when anything goes wrong in the national airspace system.

O’Hare’s heavy reliance on United and American means that any FAA-imposed constraint quickly multiplies. United, which controls the largest share of gates and departures at the airport, has already seen multiple nationwide ground stops over the past year linked to technology outages in its Unimatic flight data system, each one triggering hours of cascading delays and cancellations. American, which is locked in a broader battle for gates and growth at O’Hare, has been equally exposed when visibility drops, de-icing slows departures or air traffic control centers impose flow restrictions that cut the rate of arrivals and departures per hour.

While today’s ground stop at O’Hare was not as severe or prolonged as previous national-level technology failures, it hit at a time when schedules are already compressed by FAA-mandated flight reductions and winter storm vulnerabilities across the Midwest. Passengers reported long lines at rebooking desks, with many United and American flights pushed back by 60 to 120 minutes as the airport worked through backlogs of arriving and departing traffic.

Fog Triggers a Ground Stop at Miami International

At Miami International Airport, a dense blanket of morning fog prompted the FAA to order a ground stop for all incoming flights on Wednesday, January 14. The ground stop, which went into effect around 8:30 a.m. local time, was triggered by what officials described as low ceilings and sharply reduced visibility across parts of South Florida. Both American and United, which operate significant schedules into Miami, were among the airlines forced to hold or delay flights bound for the airport.

The National Weather Service had issued a dense fog advisory for Miami-Dade, Broward and Palm Beach counties, warning that visibility on the ground could shrink to less than half a mile. Those same conditions translate into major safety concerns for arriving aircraft, particularly in a busy morning arrival bank when airspace and runway usage are already at a premium. FAA controllers responded with a ground stop, ordering airports around the country to keep Miami-bound flights on the ground until conditions improved.

By about 9:30 a.m., as the fog began to lift and visibility improved, officials at Miami International confirmed that the FAA had lifted the ground stop and that arrivals were gradually resuming. Even so, the one-hour interruption was enough to force dozens of morning flights into holding patterns on the ground at their origin airports. American Airlines, the dominant carrier at Miami, saw knock-on delays across its Florida and Caribbean network as inbound aircraft were held and departure banks had to be resequenced. United, with a smaller but growing footprint in Miami, reported delays on multiple domestic connections into the South Florida hub.

Impact on American Airlines and United Airlines Operations

For American Airlines, the Miami ground stop could hardly have come at a more inconvenient time. The carrier has been leaning heavily on its Miami hub to serve resurgent demand across Latin America and the Caribbean, especially after the FAA lifted earlier airspace restrictions linked to military tensions around Venezuela and neighboring regions. A fog-related shutdown of incoming traffic, even for an hour, forced American to juggle arriving widebody and narrowbody aircraft, reshuffle gate assignments and resequence outbound departures to high-demand leisure markets.

United Airlines, meanwhile, continues to grapple with the reputational and operational hangover of multiple technology-related disruptions that have drawn close scrutiny from regulators and travelers alike. In August 2025, a major failure of the airline’s Unimatic system prompted the FAA to approve a ground stop that halted United departures at key hubs including Chicago O’Hare, Denver, Houston and Newark. More than a third of United’s network was delayed that day, with thousands of flights affected and passengers stranded across the country.

That history has colored how travelers view any new FAA restriction involving United’s hubs, especially when it coincides with broader weather or airspace issues. Even when a ground stop is driven by conditions outside the airline’s direct control, such as fog in Miami or winter storms in Chicago, customers are increasingly wary of the potential for prolonged disruption. United has emphasized that its most recent technology issues were resolved within hours and that they did not involve cybersecurity breaches, promising to treat such events as controllable delays that qualify for hotel and meal compensation where applicable.

American Airlines has been more focused on structural issues at O’Hare, where it is contesting a city decision that would shift additional gates to United. The carrier argues that the reallocation would unfairly limit its growth potential at the airport. The immediate effect for travelers, however, is that American has less flexibility than United to rebuild schedules and recover from FAA-imposed ground stops or capacity reductions, particularly during peak travel banks.

Why the FAA Uses Ground Stops

A ground stop is one of the most powerful tools the FAA can deploy when safety or system stability is at risk. When a ground stop is ordered for an airport, flights destined for that airport are held at their origin and are not granted departure clearance until the restriction is lifted. The measure is designed to prevent aircraft from converging on a congested or unstable airspace where controllers and airport infrastructure may not be able to handle additional arrivals safely.

Ground stops are typically issued for three broad reasons: severe or rapidly changing weather near an airport, major operational disruptions such as technology failures at an airline or an FAA facility, or unexpected hazards including security incidents. Weather remains by far the most common trigger. Low visibility from fog, wind shear, strong crosswinds or thunderstorms can all reduce the number of aircraft that can land and take off safely in a given period, forcing the FAA to meter traffic or, in extreme cases, halt it entirely.

The essential principle behind a ground stop is that it is better to keep aircraft on the ground at their point of origin than to have them circle for extended periods near their destination, burning fuel and potentially diverting to alternate airports. Once conditions improve or the underlying problem is resolved, the FAA lifts the stop and controllers gradually rebuild the normal flow of traffic. The downside for travelers is that even a short ground stop can create a chain reaction of delays and missed connections that last for many hours.

Broader Strain on the U.S. Air Travel System

Today’s disruptions in Chicago and Miami come on top of structural challenges that have been building in the U.S. air travel system over the past year. Since November 2025, the FAA has been implementing a temporary 10 percent reduction in flights at 40 major airports nationwide as part of its response to staffing shortages and pressures created by the prolonged government shutdown. Those reductions have lowered the theoretical maximum capacity of key hubs, giving controllers more breathing room but leaving airlines with fewer slots to absorb irregular operations.

For American and United, both heavily reliant on banks of closely timed arrivals and departures at their hub airports, that systemwide constraint has made it harder to recover quickly from local disruptions such as today’s fog in Miami or winter weather in Chicago. Each canceled or delayed flight can create a ripple effect, as aircraft and crews arrive late for their next scheduled segment or miss tightly timed connections. When schedules are already trimmed by 10 percent, there are fewer backup aircraft and crew options to plug those gaps.

Travelers are feeling the difference. Data from recent months has shown elevated levels of delays and cancellations at major hubs even on days without headline-grabbing storms or outages. Airlines have responded by padding block times on key routes, increasing minimum connection windows at congested airports and rolling out more generous travel waivers in anticipation of weather or system stress. Still, the FAA’s use of targeted ground stops remains a necessary safety valve when the system approaches its limits.

How Travelers at Chicago and Miami Are Being Affected

At terminal level, the human impact of today’s ground stops in Chicago and Miami was immediately visible. At Miami International, passengers on early morning arrivals were held at departure airports across the country, with airlines delaying boarding or keeping passengers on the ground while they waited for clearance from the FAA. Once the stop was lifted, a rush of inbound flights hit the airport nearly simultaneously, crowding gate areas and forcing some aircraft to wait on taxiways for open positions.

American Airlines agents in Miami spent much of the morning reworking connections for passengers bound for Caribbean and Latin American destinations whose flights had missed their slots due to the fog-related delays. Some travelers received same-day rebookings, while others were offered hotel accommodations and meal vouchers if their new departure times stretched into late evening. United passengers connecting through Miami to transcontinental or northeastern flights also reported needing new itineraries.

In Chicago, the situation was compounded by the cumulative effect of earlier storms and lingering FAA capacity constraints. Travelers at O’Hare described long lines at customer service counters for both United and American, with some domestic flights delayed two hours or more during the mid-morning and midday banks. International services were generally prioritized, but any misalignment in arrival times meant that onward domestic connections were often missed, leading to crowded standby lists and, in some cases, overnight stays.

What Passengers Can Expect in the Coming Days

Although the Miami ground stop lasted roughly an hour and operational restrictions at Chicago O’Hare today were less severe than in prior months, the aftershocks are likely to linger through the evening and potentially into tomorrow for some travelers. Airlines typically need several schedule waves to fully recover from a disruption, particularly when aircraft and crews are scattered across multiple hubs.

Both American and United have urged customers traveling through Chicago and Miami to monitor their flight status closely and to make use of mobile apps and text alerts for the most current information. Same-day travel waivers have become more common, allowing passengers to move to earlier or later flights without change fees when weather or FAA decisions significantly affect schedules. For those with tight connections through O’Hare or Miami, airlines are recommending longer layovers where possible, especially during the early morning and evening peak periods when air traffic is densest.

The events of today also reinforce a broader reality for U.S. travelers in 2026. With the FAA operating under unusual strain from staffing shortages and the reverberations of the government shutdown, and airlines still working through their own technology and fleet challenges, even seemingly minor disruptions can have outsized effects. Ground stops at major hubs like Chicago O’Hare and Miami International may remain an occasional but disruptive feature of the travel landscape in the months ahead, placing a premium on flexibility, contingency planning and real-time information for anyone heading to the airport.