An airline seat is a seat on an airliner in which passengers are accommodated for the duration of the journey. Such seats are usually arranged in rows running across the airplane's fuselage. A diagram of such seats in an aircraft is called an aircraft seat map.
On the oldest of planes, seats were which stood loosely in the cabin, but movable furniture in the aircraft is a safety hazard, and seats are now fastened to the floor. However, airlines usually want the flexibility to move seats around or remove them, so the seats are attached to rails underneath the floor which run along the aircraft fuselage. If the airline wants to reconfigure the seating, this is a minor operation.
For passenger safety, airline seats are equipped with seatbelts, and there is a "Fasten Seatbelts" sign above each seat which is lit up when passengers are expected to remain seated with the seatbelt fastened. This is during taxiing, take-off and landing, although turbulence may also prompt the captain to turn on this sign.
Seats are frequently equipped with further amenities. Airline seats may be equipped with a reclining mechanism for increased passenger comfort, either reclining mechanically (usually in economy class and short-haul first and business class) or electrically (usually in long-haul first class and business class). Most aircraft also feature trays for eating and reading, either in the seatback which folds down to form a small table in most economy class seats, or inside the armrest which folds out in most first class, business class, bulkhead, and exit row seats. Most airline seats also feature a pocket which may contain an in-flight magazine and safety instructions.
On small and short-haul aircraft, or on low-cost carriers, some of these amenities may not be installed. For instance, on several aircraft, Ryanair has installed non-reclining seats without seat pockets with the safety manuals stitched to the seat back instead. Even on airliners with reclining seats, some seats may have a restricted recline or no recline. Typically this will be the rear row of the cabin where a rear bulkhead blocks the recline, or seats immediately in front of the emergency exit where a reclined seat might restrict access to the emergency exit, creating a potential safety hazard. Independent seat review sites such as SeatGuru often warn passengers against these seats. During take-off and landing the crew ask passengers to put their seats in an "upright" (unreclined) position and to lift and stow their tray tables.