400+ SFO Flights Delayed After East Coast Air Traffic Control Outage

San Francisco International Airport saw more than 400 flight delays on Monday, September 21, 2026, as a major air traffic control outage in the U.S. Northeast disrupted flight flows and triggered nationwide ripple effects across airline networks.

What happened: Northeast outage triggered ground stops and diversions

Published coverage shows the disruption centered on the Philadelphia Terminal Radar Approach Control facility, commonly known as Philadelphia TRACON, which manages critical airspace and arrival sequencing for multiple busy airports in the New York and Philadelphia region. The incident led to restrictions that slowed or temporarily halted inbound traffic at key airports, creating immediate congestion both in the air and on the ground.

Reports indicate damaged communications lines were a primary factor in the outage. Flight disruptions were particularly severe at Newark Liberty International Airport, where flight-tracking data cited in national coverage showed arrivals were effectively halted for hours, turning one of the country’s most delay-prone hubs into a bottleneck for the rest of the system.

While some operations began resuming later in the day, the timing mattered: late-morning through afternoon interruptions on the East Coast tend to cascade into evening schedules nationwide, because aircraft and crews are often scheduled to operate multiple legs across time zones.

Why SFO was hit: network knock-on effects reached the West Coast

Even though the outage occurred thousands of miles away, SFO’s schedule is tightly linked to East Coast hubs through long-haul transcontinental routes and banked connections. When aircraft cannot arrive into the New York and Philadelphia region on time, the same airplanes often cannot depart back to California as scheduled, and crews can run out of available duty time.

Local Bay Area coverage described more than 400 delayed flights at SFO on Monday, with impacts compounded by SFO operating under an FAA ground-delay program tied to low ceilings, limiting arrival rates during part of the day. That combination meant travelers faced both upstream disruptions from the Northeast and local arrival constraints at SFO.

For passengers, the result at SFO often looks like a rolling series of gate holds, late inbound aircraft, and missed connections, especially for itineraries routing through Newark, New York-area airports, or Philadelphia. In many cases, the delay on a single inbound aircraft can affect multiple later departures from the same gate.

Most affected airports and airlines: Newark and Philadelphia at the center

National reporting and flight-tracking summaries indicated the New York City-area airport system was broadly affected, with Newark among the hardest hit. Newark’s role as a major United Airlines hub makes disruptions there particularly likely to spread quickly to other cities, including San Francisco, because it is a key transfer point for domestic and international connections.

Published coverage also pointed to Philadelphia’s importance as a hub airport, with knock-on impacts to schedules of multiple carriers. When arrival rates are constrained at hub airports, airlines may preemptively cancel or delay flights to manage aircraft positioning and avoid gridlock.

Airline advisories and exception policies posted publicly during the disruption showed carriers offering flexible rebooking for certain affected travel dates and airports. Travelers impacted by Monday’s delays and cancellations have typically been advised to check their airline’s rebooking options, monitor app notifications closely, and confirm whether their itinerary includes airports subject to air traffic flow restrictions.

What travelers can do now: practical steps for SFO departures and connections

For travelers flying out of SFO over the next day or two, the most useful first step is verifying whether the inbound aircraft for your flight is already delayed, because that often predicts a late departure hours before the airport departure board does. If you are connecting to the Northeast, it can also help to check whether your destination or connecting airport is still experiencing residual delays from aircraft and crew repositioning.

When disruptions are tied to air traffic control constraints, airport operations can shift quickly. A flight may show an early delay estimate that later increases, or it may recover time if traffic management initiatives are lifted. Keeping baggage to a carry-on, when feasible, can reduce rebooking friction if a connection is at risk.

Passengers concerned about tight connections should consider requesting same-day flight changes when available, including reroutes through less-congested hubs. For example, a traveler booked SFO to Newark might find more reliable options by connecting through another airport if seats are open, though availability may be limited during systemwide disruption events.