If you can choose when to fly, choose early. Delays build up as the day goes on, and an early flight that does go wrong leaves you the most later flights to fall back on. There are a few exceptions worth knowing about.
Why delays build through the day
Most aircraft fly several trips a day, and so do their crews. The first departure of the morning usually starts with an aircraft that has been parked overnight and a crew that is fresh, so there is nothing earlier in the day for it to inherit.
From then on, every late arrival makes the next departure late. A 30 minute hold-up in the morning can still be showing up as a delay in the evening, several flights later. That is why "late arriving aircraft" is one of the most common reasons airlines give. It also means the stated cause of your evening delay may have nothing to do with your airport. (See what to do when your flight is delayed for how to find the real reason.)
Weather has a daily pattern too
In summer, thunderstorms build through the afternoon across much of the country, and lightning near an airport stops work on the ramp. Airports where afternoon storms drive many delays include Orlando, Atlanta, Dallas Fort Worth and Denver. A morning departure from any of them usually gets out before the storms start.
The exception: morning fog and low cloud
Some airports have the opposite problem. Low cloud and fog are most common in the early morning and reduce how many aircraft can land each hour. That mostly affects arrivals, and the flights those arriving aircraft are due to operate next.
- San Francisco: low cloud and closely spaced runways mean the FAA often holds inbound flights at their origin.
- San Diego and Los Angeles: the coastal marine layer, mostly in late spring and early summer.
- Seattle-Tacoma and Salt Lake City: fog in fall and winter.
Early departures from these airports are still a good choice. What to avoid is a tight connection that depends on an early-morning arrival into one of them.
Avoid the last flight of the day
If the last flight to your destination is cancelled, there is nothing left to move to until tomorrow. If your trip matters, book a flight that leaves at least one or two later departures on the same route as a backup. That applies just as much to the second leg of a connection.
Season and day of week
- Summer brings the afternoon storms described above and the fullest flights, so there are fewer empty seats to rebook into.
- Winter brings snow, ice and de-icing queues at northern hubs. These are worst in the early morning after an overnight storm.
- Hurricane season (June to November) can shut Florida and Gulf Coast airports for days. Airlines usually announce travel waivers before a storm arrives.
- Holiday peaks and Sunday evenings run with very full flights, which makes rebooking slower if something goes wrong.
Already booked a later flight?
You do not have to change it. Instead:
- Note the next one or two flights on your route, on your airline and others, so you know your backups in advance.
- On the day, check where your aircraft is coming from. If the inbound flight is running late, yours will be too.
- If a big storm is forecast, look for a travel waiver that lets you move to an earlier flight at no charge.
The rest of the preparation is in the pre-trip checklist. If you are connecting, also read how long a layover should be.
This guide is general information for US travelers, not legal advice. Rules and airline commitments change; check with your airline or the US Department of Transportation for your specific situation.