Fighter

Fighters are a category of combat air- and spacecraft smaller than corvettes or cutters. Fighters can be broadly divided into atmospheric fighters and space fighters (or exoatmospheric fighters), though with technological progress, hybrids of the two categories have become increasingly viable. Other categories include the aerospace fighter, intended to extend a capital ship's power-projection capability from the vacuum into an atmosphere, as well as the deep-space fighter, intended to perform incursions outside a planet's orbit, but rarely interplanetary distances. Space fighters have historically also been known as gunboats or missile boats, such terms are now generally used to refer to fighter craft on the larger side.

Fighter spacecraft are sometimes dubbed starfighters in the media and corporate contexts, though this term is rarely used in the actual military and is generally regarded as quaint.

Tactics and doctrine
In an atmosphere, fighter craft dominate the battlespace. In space, they are used to extend the protection and reconnaissance screen of a larger ship or fleet. Though superficially similar to atmospheric fighters, space fighters are technically more analogous to seaborne gunboats as they occupy the same medium as the larger ships. Many types of space fighter have thus historically developed to operate in niches such as low orbit and within a planet's atmosphere, allowing the larger ship to hang back in a higher orbit. UNSC space fighters are typically dominated by a generalist design philosophy exemplified by the GA-TL1 Longsword series, which, in addition to serving as an interceptor and strike fighter, can double as a surface bomber and even search-and-rescue craft.

Unmanned fighters are used in roles considered too risky for human pilots, or ones requiring only simple instructions. Drones can endure faster accelerations than manned craft and are far more disposable, allowing precious mass and space to be taken up by propellant and weapons; such craft are usually little more than missile buses or glorified missiles themselves. Many models of manned fighter craft, such as the Longsword, can also be remotely operated on missions that require no human presence (or are regarded as too risky for human pilots). Fighters may also be used as command craft to direct drone squadrons.

Aerospace fighters operate primarily within an atmosphere, with air-breathing jets as their primary engines, though some examples are capable of limited vacuum flight (usually with a dedicated rocket engine with enough fuel for a return trip to low orbit). They are an important asset of aerospace control, as larger starships cannot descend too far down into a gravity well. However, their effectiveness decreases the further out of atmosphere you go, and in deep space they are easily bested by dedicated gunboats and outright warships, whose point defenses and missiles are able to pick off incoming fighters before they can do much damage. Aerospace fighters may be launched from surface-based platforms or orbital carriers, and often use launch-assist systems when conducting an orbital mission from a planet; launching from an Earth-sized planet is very taxing for a fighter's propellant reserves, which will limit the craft's missions endurance once in space.

Fighter battles in space are largely fought between fighters, or with a fighter squadron against small ships such as cutters and corvettes, whose point defenses fighter swarms are able to still comfortably overwhelm. Fighters also operate as support for a warship such as a frigate or cruiser in one-to-one combat scenarios. However, they can contribute little to large-scale fleet engagements outside peripheral roles.

Fighter combat in space has little to do with aerial combat and even less with the traditional pop culture image of dogfighting. Similar to combat between larger ships, relative velocities between opposing craft are usually measured in multiple kilometers per second. Missiles dominate at long ranges, and any close-range clashes are mostly brief flashes of action as combatants speed past one another. In some cases, however, spatial fighter combat may occur in the same or relatively close moving reference-frame, resulting in more conventional "knife-fight" clashes between fighters; this became particularly common during the Human-Covenant War due to the Covenant's tendency to drop their fighter craft from a carrier craft in slipspace into close proximity to their target at a similar overall vector, partially or fully circumventing the UNSC's preferred long-range missile strikes.

The Covenant use space fighters in a more conventional manner than the UNSC because their anti-AI dogma bans most autonomous drones or automated targeting and firing systems, with the effectiveness of their missile guidance systems also being limited. In addition, Covenant plasma weapons are most effective at close ranges, especially on a fighter scale. The Sangheili have a long and proud history of dogfighting, which lent itself well to this paradigm. Due to the split-second reaction times required in space combat, Covenant fighter pilots use neural interface-based controls to avoid input lag.

History
Traditional dogfighting in particular has historically not played a large role in UNSC doctrine. One of the biggest adversaries to the development of true strike fighters or dogfighters are guided missiles. While the engagement distances between even other fighters could be measured in tens of kilometers, missiles meant that any potential opponent could wipe you out well before you could get into range with conventional guns. Although countermeasures do provide a reprieve, they don't usually matter until they are deployed literally seconds before impact, as most guidance systems (especially those coordinated by an AI or mothership) are very good at picking decoy to actual target. So the theory for counter-fighter engagement is to bring as much payload to bear as you can, while minimising the enemy's ability to target you via ECM or interference by other craft.

The most obvious candidates for interceptors were either heavy bombers equipped with enhanced sensors and as many anti-fighter missiles they could carry (such as the Longsword), or small, short-range interceptors designed for extending a fleet's protection screen. To get an elite fighter close enough to destroy them without being annihilated at some point was not only madness, but suicidal. Swarms of drones and missiles could be utilized in this role, but these lacked the versatility of human-piloted craft. Most space fighters up until the 26th century were multirole combat craft larger than traditional fighter jets, usually labeled as either gunboats or missile boats. Unlike the Longsword and other later types, such craft were often non-aerodynamic, being fully optimized for vacuum operations.

The Human-Covenant War and the Covenant's abundant use of fighter tactics the UNSC looking more into developing a compact aerospace superiority fighter, as the Longsword was deemed too large and clumsy to contend with Seraphs and Banshees dropping right on top of them. One of the things hampering UNSC fighter development was the fact that many naval officers were not convinced that smaller nimble fighter craft were necessary to the war effort. Most of them just saw fighter development programs as boondoggles that diverted resources from more important projects. However, other officers, particularly those who had flown the Longsword and similar craft into battle, pushed for the development of strike fighters as a counter to Covenant close-range fighter tactics. They were joined by UNSC Aerospace Force officers who really wanted a fighter that could take the fight out of the atmosphere. As long as Seraphs and other classes of strike fighter could climb above an air-breathing vehicle's operational ceiling, the Aerospace Force were at a disadvantage. This led to the development of the Sabre, often regarded as the UNSC's first dedicated "vacuum dogfighter".

UNSC

 * Crow — an older, lightly-armored space fighter popular in the commercial sphere as a convoy escort and anti-piracy craft.
 * Baselard — a 25th-century vacuum-only craft mainly used for orbital engagements and limited deep-space interception missions. Later mostly replaced by the Longsword.
 * Broadsword — atmospheric fighter and ground-attack craft. Capable of being inserted from orbit, but requires external launch aid for STO.
 * Longsword — introduced in 2521, the Longsword is a mainstay general-purpose fighter-bomber. A high-endurance craft, the Longsword is able to perform a wide variety of missions, which makes it ideal for Navy use. Is capable of a single SSTO transit before refueling, and is able to perform deep-space incursions.
 * Nandao — a small, fast and nimble strike fighter specialized in extending a carrier's force-projection capability into a gravity well and atmosphere, possessing the capability for a single dip into an atmosphere and back.
 * Sabre — a small and super-maneuverable orbital defense craft developed in response to Covenant fighter tactics, the Sabre is space-optimized and designed to use external booster packages to climb to orbit to save onboard reaction mass, but can re-enter and land on its own.
 * SkyHawk — aerial jump jet in service with the Aerospace Force.
 * Swift — high-endurance reconnaissance and electronic warfare craft with limited stealth capabilities.

Covenant

 * Gigas — an older model of fighter-bomber.
 * Banshee Interceptor — light fighter / skirmisher craft; larger cousin to the Banshee ground-attack craft. Limited to space-only operation.
 * Seraph — general purpose fighter-interceptor. Capable of both vacuum and atmospheric operation (including surface bombing missions), though handles more sluggishly in atmosphere.
 * Tarasque — heavy fighter capable of being used as a bomber or even dropship.