Seat downgrade

Seat downgrade refers to a situation where a passenger is moved from a higher-class cabin, such as business or first class, to a lower-class cabin, typically economy, for part or all of a flight. 

This can happen for a variety of operational reasons, including overbooking of premium cabins, aircraft changes that reduce the number of higher-class seats, or technical issues that require the airline to reassign passengers. 

Seat downgrades are usually involuntary and may provide compensation depending on airline policies and regulations, as they cause passenger dissatisfaction.