After takeoff, passengers are free to move about the cabin without fear of disrupting critical weight distribution. But that doesn't necessarily mean it's OK to take over empty seats without warning.

Moving to an empty seat on a plane is generally acceptable only if you follow specific etiquette and safety protocols. You should always wait until the "Fasten Seatbelt" sign is turned off and the aircraft has reached its cruising altitude. At that point, you must ask a flight attendant for permission before moving. Airlines often restrict moves for two main reasons: Weight and Balance (especially on smaller aircraft where seat distribution is critical for flight stability) and Class of Service (you cannot move into "Economy Plus" or "Extra Legroom" seats without paying a fee, as these are considered separate products). In 2026, some airlines like United have become stricter, with flight attendants instructed to collect "upcharge" fees via mobile tablets if a passenger moves into a premium row. Moving without permission is considered a breach of cabin safety and can lead to a formal reprimand from the crew. If the move is within the same price "tier" and the flight attendant approves, it is a great way to secure more space for a long-haul journey.