Loiter (aeronautics) in the context of Aerial refuelling

Aerial refueling (en-US), or aerial refuelling (en-GB), also referred to as air refueling, in-flight refueling (IFR), air-to-air refueling (AAR), and tanking, is the process of transferring aviation fuel from one aircraft (the tanker) to another (the receiver) while both aircraft are in flight. The two main refueling systems are probe-and-drogue, which is simpler to adapt to existing aircraft and the flying boom, which offers faster fuel transfer, but requires a dedicated boom operator station.

The procedure allows the receiving aircraft to remain airborne longer, extending its range or loiter time. A series of air refuelings can give range limited only by crew fatigue/physical needs and engineering factors such as engine oil consumption. Because the receiver aircraft is topped-off with extra fuel in the air, air refueling can allow a takeoff with a greater payload which could be weapons, cargo, or personnel: the maximum takeoff weight is maintained by carrying less fuel and topping up once airborne. Aerial refueling has also been considered as a means to reduce fuel consumption on long-distance flights greater than 3,000 nautical miles (5,600 km; 3,500 mi). Potential fuel savings in the range of 35–40% have been estimated for long-haul flights (including the fuel used during the tanker missions).

An unmanned combat aerial vehicle (UCAV), also known as a combat drone, fighter drone or battlefield UAV, is an unmanned aerial vehicle (UAV) that carries aircraft ordnance such as air-to-surface missiles, anti-tank guided missiles (ATGMs), and/or aerial bombs on hardpoints or within weapons bay, allowing it to perform tactical attacks known as drone strikes. UCAVs are used for intelligence, surveillance, target acquisition and reconnaissance, attacking high-value targets and prolonged loitering before needing to return to base, unlike kamikaze drones, which are single-use drones made for physically ramming into a target and exploding on impact; or surveillance drones, which are unarmed drones used only for aerial reconnaissance and gathering intelligence.

Aircraft of this type have no onboard human pilot, but are usually under real-time remote control by human operators, with varying levels of automation. As the operator runs the vehicle from a remote terminal via radio control, equipment necessary to support an on-board human pilot is not needed, resulting in a lower weight and a smaller size than a manned aircraft for the same payload. Many countries have operational domestic UCAVs, and many more have imported fighter drones or are in the process of developing them.

A loitering munition, also known as a suicide drone, kamikaze drone, or exploding drone, is a weapon with a warhead that is typically designed to loiter until a target is designated, then crash into it. They enable attacks against hidden targets that emerge for short periods without placing high-value platforms near the target area. Unlike many other types of munitions, their attacks can be changed mid-mission or aborted. Loitering munitions are typically aerial platforms, but include some autonomous undersea vehicles with similar characteristics.

Loitering weapons emerged in the 1980s for the suppression of enemy air defenses (SEAD) role, and were deployed for SEAD by some military forces in the 1990s. In the 2000s, they were developed for additional roles, from long-range strikes and fire support to short-range tactical systems that fit in a backpack.

The escort fighter was a concept for a fighter aircraft designed to escort bombers to and from their targets. An escort fighter needed range long enough to reach the target, loiter over it for the duration of the raid to defend the bombers, and return.

A number of twin-engined heavy fighters with high fuel capacity were designed for escort duties prior to the outbreak of World War II. Such heavy fighters largely failed in their intended escort role during the war, as they were commonly outmaneuvered by more agile single-engined fighters. As the war progressed, longer-range fighter designs and the use of drop tanks allowed single-engined fighters to perform escort duties. In the post-war era the introduction of jet engines and their inherent short range made escort fighters very difficult to build. The related concept of a penetration fighter emerged briefly in the 1950s and again in the 1960s, but did not result in any production aircraft. Parasite fighters—small aircraft designed to be carried by a specialized bomber—were seen as a possible solution to the limited ranges of most traditional escort fighters. First experimented with in WWI, the U.S.-designed XF-85 Goblin would emerge as the last dedicated parasite fighter design and was abandoned in 1949 due to technical issues as well as the advent of practical aerial refueling.