Most air traffic control delays happen because more flights want to use an airport or a piece of airspace than it can safely handle at that moment, usually because of weather. According to the FAA, weather caused about 74% of system delays longer than 15 minutes from mid-2017 to mid-2023. When capacity drops, the FAA holds flights on the ground, where waiting is safer than circling in the air.
The main kinds of ATC delays
Ground stop
Flights headed to an airport are held at their departure airports until conditions improve, often because of thunderstorms, low visibility or a runway problem. Ground stops are usually short and are updated as conditions change.
Ground delay program
When an airport can land fewer planes per hour than are scheduled, flights headed there get assigned takeoff times, called EDCTs, to spread out the arrivals. If your pilot mentions an EDCT, you'll usually wait at the gate instead of in the air.
Airspace flow program and reroutes
When storms block a busy stretch of sky, flights through it are metered or sent on longer routes around the weather.
Miles in trail
Controllers space arriving flights further apart so a busy airport or sector doesn't get overloaded. It can mean a slower climb, a longer route or a short wait before takeoff.
Is it the airline or ATC?
U.S. airlines report delay causes to the Department of Transportation in five groups: the airline itself, extreme weather, the National Aviation System (which includes air traffic control, non-extreme weather and heavy traffic), a late-arriving aircraft, and security. If your app says "ATC" or "National Airspace System," the delay is tied to traffic management, which is often weather somewhere along your route.
Why a sunny day can still mean delays
Your airport can be clear while your destination has low clouds, the airspace in between has a line of thunderstorms, or your plane is still stuck somewhere else. One storm system can ripple delays across the whole country.
What controllers are doing during a delay
At the FAA's Air Traffic Control System Command Center in Virginia and in traffic management units at facilities across the country, specialists rebalance thousands of flights to match what the weather allows. Meanwhile, controllers keep every aircraft already in the air safely separated. A delay on the ground is the system choosing safety.
Tips for delayed travelers
- Check the airport, not just the flight. Our live delays page shows FAA ground stops and delay programs as they happen.
- Stay near the gate. Ground stops can lift early, and boarding can start fast.
- Look at the big picture. Storms at your destination or along the route matter as much as your own weather.
Delays are frustrating, but every one of them is a team keeping flights safely apart. Once you land, a quick thank-you goes a long way.
Common questions
What is a ground stop?
An FAA order that holds flights headed to an airport at their departure airports, usually because of weather or a runway problem at the destination.
How long do ground stops last?
Often from about half an hour to a few hours. The FAA updates them as conditions change and can lift them early.
What is an EDCT?
An Expect Departure Clearance Time: an assigned takeoff time used during a ground delay program to spread out arrivals at a busy airport.
Does air traffic control cancel flights?
No. Airlines decide whether to cancel flights. ATC manages the flow of traffic, which can lead airlines to cancel when delays get long.
What causes most flight delays?
For system-wide ATC delays, weather. The FAA reports weather caused about 74% of delays over 15 minutes from 2017 to 2023.