Also known as a flight segment, a flight leg is an airline industry term for a flight that maintains the same flight number and aircraft throughout its journey from one airport to another.
In other words, it’s a direct flight from point A to point B with no stops or changes of aircraft along the way. This flight may be one of multiple segments of an itinerary involving one or more layovers and/or changes of aircraft. With rare exceptions, every flight you take is an individual flight leg. If you board the plane in one city and get off in another city, that's a flight leg.
You can skip a leg of your flight, but it’s important to note that as soon as you no-show, the airline will cancel any legs after the once you’ve skipped, including any return flights if they’re on the same itinerary.
Intentionally missing a leg of your itinerary is a key component of a money-saving travel hack called hidden city ticketing. Instead of looking for direct flights to their intended destination, passengers search for deals that include a layover at their intended arrival airport regardless of the itinerary’s final destination.
When they arrive for a layover in the city they want to stay in, they simply exit the airport instead of boarding the next flight leg. This can be a money-saving tactic due to something called “hidden city ticketing,” wherein an airline might sell a multi-stop itinerary connecting, for example, New York to Denver with a layover in Charlotte, at a lower cost than a direct flight from New York to Charlotte.
Skipping a flight leg is not illegal but it is frowned upon by airlines. Passengers who frequently miss connecting flights as a part of this strategy can face retaliation from the airline like invalidated frequent flyer miles or loss of elite status. Additionally, as mentioned above, an airline will cancel any legs after the leg you’ve skipped.
When a flight is diverted due to weather or other unforeseen events, an aircraft might be rerouted to a different arrival airport than originally scheduled. A “flight recovery leg” is an industry term for the new flight segment created to deliver passengers to their intended arrival destination after an unexpected rerouting.