They will often wait a little while, especially if it's the last flight of the day and even moreso if there are multiple passengers making the same connection. I've had Delta wait for me after inbound connection delays on several occasions.

Generally, in 2026, airlines do not delay flights for individual connecting passengers, as the cost of a delay (fuel, crew hours, and missed slots) far outweighs the cost of rebooking a few people. However, there are two major exceptions. First, if a large group (e.g., 20+ people) is coming from a single delayed flight and heading to the same connection, the airline may "hold" the plane for 15–30 minutes if it doesn't cause them to lose their takeoff slot. Second, if the flight being held is the last flight of the day on a low-frequency route, the operations center is more likely to wait to avoid expensive hotel vouchers for stranded passengers. In 2026, predictive AI helps airlines decide in real-time whether a delay is "worth it." If your flight is "airline-protected" (on one ticket), the airline is legally obligated to rebook you for free if you miss your connection, but they prioritize the schedule of the 200 people already on the plane over the one or two who are running late.