When a flight itinerary requires a traveler to change planes, the flights are called connecting flights.
The answer here depends a great deal on your itinerary. For connecting domestic flights, you almost never have to exit and reenter security, though there are some exceptions at airports where the terminals aren’t all connected.
For domestic-to-international connection, it's still pretty rare that you have to exit and reenter security, even if you're changing terminals. Most (but again, not all) airports connect international terminals airside.
When you’re connecting from an international flight to a domestic one, you’ll always have to exit and reenter security as you’ll need to go through customs and immigration (unless you have gone through preclearance aboard, which is rare).
Not usually. In some rare cases, if you’re traveling with a big group that happens to be a large portion of the connecting flight’s passengers, an airline may choose to hold a flight for the incoming group—and in fact United is testing a program that would help them determine when to do so—but don’t count on it.
This again depends on your itinerary. If you’ve booked the flights on a single itinerary and the first flight is delayed, the airline will put you on the next available flight.
If you’re traveling on two different itineraries (meaning you booked two flights through two different systems) and a delay in your first flight causes you to miss the second, that’s more problematic. The second airline has no knowledge of your first flight—to them, you’re simply someone who didn’t show up. They may accommodate you with a seat on the next available flight, and they may not. In that case, you’ll need to book another ticket.
This varies quite a bit by airport and the type of connection (domestic or international) you’re trying to make. If the airport layout requires passengers to exit one terminal and enter another between flights (often the case with international connections), that may mean going through security a second time—which may take a while. If you’re traveling on two different itineraries, you’ll need to allow for additional time to go through baggage claim (if you’re checking a bag) and security between flights.
In most cases, one hour should be enough for a domestic-to-domestic connection or a domestic-to-international, but check the airport’s website for a minimum suggested time to allow for a connection. If you’re connecting from an international flight to a domestic one, however, you could need a few hours, as we’ll explain below.
When you’re traveling internationally, you will need to go through border control/immigration and customs at some point, usually your first point of entry in that country. So, if you’re traveling to the United States from another country, you’ll have to collect your bags, go through customs and immigration, and re-check your bags before heading to your connecting flight, which may be in another terminal.
While these terms are often used interchangeably, they are not the same thing. A layover is the time you spend at the airport between two flights. A connecting flight is the next flight in your itinerary that you’re waiting at the airport to take.
If you’re traveling internationally to the US, you’ll need to collect your baggage upon your first entry in the US, and go through customs and passport control. You’ll then re-check your bags before continuing through the airport for your connecting flight (you won’t have to pay to re-check them for the domestic legs if you had a free international checked bag allowance or if you already had to pay for your checked bag internationally).
If you’re traveling domestically or internationally on a single itinerary, your bags will typically be checked through to your final destination. If you’ve booked the flights separately though, you’ll need to collect your bags after the first flight and recheck them.
Yes. You’ll probably get all boarding passes at once when you check in for your first flight, whether you check in online, on your smartphone, or at the airport. For some international itineraries though, the airline will direct you to get your second boarding pass on your layover.
Technically, yes, but if you skip a flight on a multi-flight itinerary, any subsequent flights on your itinerary will be canceled—including your return flights.
It’s also important to note that if you skip your connecting flights often, the airline may impose penalties such as voiding your frequent flyer miles. The topic is a complex one, so read more in our guide to hidden-city ticketing.