If there are not enough passengers who are willing to give up their seats voluntarily, an airline may deny you a seat on an aircraft based on criteria that it establishes, such as the passenger's check-in time, the fare paid by the passenger, or the passenger's frequent flyer status.

Yes, airlines have the legal right to "involuntarily bump" passengers from an overbooked flight, a practice known as Involuntary Denied Boarding. However, strict regulations—such as those enforced by the US Department of Transportation (DOT) and EU 261/2004—govern how this must happen. Before bumping anyone, the airline must first ask for volunteers who are willing to give up their seats in exchange for compensation (vouchers, cash, or miles). If no one volunteers, the airline uses a set of "boarding priority" rules (usually based on check-in time, fare class, or loyalty status) to decide who to bump. If you are bumped involuntarily, the airline is often legally required to provide cash compensation that can be up to 400% of your one-way fare, depending on how long you are delayed. It is important to note that since 2017, many US airlines have adopted policies that prevent them from removing a passenger who has already boarded and taken their seat, unless there is a safety or security issue. If you are bumped, the airline must also provide a written statement explaining your rights and the compensation owed.