The gameplay of Ace Combat 5 is divided into three modes: a campaign mode, an arcade mode, and an optional tutorial. Unlike its predecessors, AC5 does not include a multiplayer mode as developers did not have enough extended time to implement one. Like previous games in the series, Ace Combat 5 features gameplay that is a cross between that of an arcade flight game and that of a flight simulator.
The game features more than fifty licensed jet aircraft, including military and experimental aircraft from the United States, Europe, and Russia. The game's planes are divided into fighter, attacker, jammer and multirole categories. The game's aircraft feature some differences in their handling that reflect their real-world capabilities, although these distinctions are not as severe as they are in reality. The game's main superfighters are the X-02 Wyvern from Ace Combat 04 and - for the first time as a playable unit - Ace Combat 2's ADF-01 Falken, which players can unlock by destroying specific mission targets. It is revealed in the 2011 franchise artbook Aces At War: A History that a plane called the ADA-01 Adler was supposed to be included in the game as a third superfighter, but gameplay balance issues and problems with programming the aircraft so close to the game's release deadline scuttled the inclusion (the Adler would become a playable vehicle in a 2016 update for Ace Combat Infinity).
Most of the game's planes are inaccessible at the game's start; planes must both be unlocked and purchased to be used in the game's campaign mode. Certain planes are unlocked as the player progresses in the campaign, while others are unlocked via the game's "technology tree" system. In this system aircraft are grouped into "families", and earning a certain number of kills with a particular plane can unlock one or more variants or derivatives within that aircraft's family. After an aircraft is unlocked, it can be purchased for use in the campaign by spending credits that are awarded according to the player's performance during missions. Unlike Ace Combat 4, there is only one type of special weapon available for each aircraft, something that critics often pointed to.
The game's heads-up display includes a radar display and other flight instrumentation, as well as displays for the plane's damage rating and available weaponry. During gameplay, an aircraft's default weaponry typically consist of a supply of guided missiles and a gun. Additionally, each aircraft is also armed with a particular special weapon, examples of which include various types of air-dropped bombs and specialized air-to-air or air-to-ground missiles.
AC5 introduces minor improvements to the game's radar display such as analog scaling of the mission map and color-coding of enemies to indicate damage level. The game also introduces to the series optional side games such as midair refuelings, which are available before and after certain missions.
In addition, Ace Combat 5 is the first in the series to feature wingman interaction. During most campaign missions, the player can issue orders to the AI members of his or her unit using the DualShock controller's directional pad. The player also must purchase and assign aircraft for each of the squadron's pilots prior to each mission. Additionally, players may choose to respond to YES/NO questions during missions by squadron mates or other characters in the game. Although the player's response or lack thereof may affect the game's dialogue, the effect these questions have on gameplay is minimal, although the player's answer will affect which one of two missions they will undergo at two different points of the game.
In addition to the main campaign, the game features an arcade mode in which the storyline has been greatly reduced in favor of gameplay. The basic plot of arcade mode is a continuation of the narrative from Ace Combat 04: Shattered Skies. The player assumes the role of Mobius One, the player character from Shattered Skies. Assisted once again by the crew of AWACS SkyEye, Mobius One is assigned to destroy the military capability of "Free Erusea", a resistance organization that formed after the conclusion of Ace Combat 04.
Basic gameplay in arcade mode remains the same as in the campaign, although certain new rules take effect. There are a total of sixteen stages in arcade mode, although only seven can be played in one playthrough due to branching mission paths. The player begins each stage with a set amount of time and a target number of enemy units that must be destroyed. The player must destroy the specified number of enemies before time expires in order to advance to the next stage. Although the player begins with a limited amount of time, each target the player destroys adds time to the clock and also awards the player a set number of points. The player's weaponry is more restricted in arcade mode than during the campaign; although destroying certain marked targets replenishes the player's stock of weaponry, the player can still end up without any if they waste too much ordnance.
Ace Combat 5: The Unsung War takes place in the year 2010. According to the game's backstory, war had previously broken out in the game world in 1995, fifteen years prior to the events of the game. In this war, detailed in the game's prequel Ace Combat Zero: The Belkan War, the bellicose nation of Belka aggressively attacked its neighboring countries in an expansionist manner. The war turned against Belka, however, and the nation faced defeat under the combined forces of the superpowers Osea and Yuktobania, along with other nations. In response, Belka set off seven nuclear weapons on its own cities in order to stave off the advancing enemy. Following this catastrophe, the opposing nations vowed to disarm. In the war's aftermath, the former state of South Belka became a protectorate of the Osean Federation, although Belkan citizens remained hostile to Osean occupation.
The player character is a member of an Osean Air Force squadron stationed on Sand Island, located on the ocean which separates Osea and Yuktobania. Although initially thought of as an island isolated from civilization, Sand Island serves as a front line during the events of Ace Combat 5 after the "fragile peace" established between Osea and Yuktobania during the previous war comes to an end.
The player character is an Osean fighter pilot known by the callsign "Blaze", and known alternatively by one of his comrades as "Kid". The player's tough squadron mates throughout most of the game include Kei Nagase ("Edge"), a female pilot with an interest in the Demon of Razgriz legends; Alvin H. Davenport ("Chopper"), a brash and talkative pilot; and Hans Grimm ("Archer"), a rookie pilot unsure of his flying skills. They collectively form a fighter squadron known alternatively as Wardog Squadron or Sand Island Squadron. As of the beginning of the game they are still pilots-in-training (nuggets), under the command of Captain Jack Bartlett ("Heartbreak One"). Bartlett had previously seen conflict in the earlier Belkan War, and during the time had formed a relationship with a female Recon Major in the Yuktobanian army, Nastasya Vasilievna Obertas.
The game also features a cast of secondary characters. Albert Genette is a freelance reporter on assignment to cover the Sand Island Squadron; he narrates much of the game's story. Captain Marcus Snow ("Swordsman") is a pilot on board the Osean aircraft carrier Kestrel, which is commanded by Captain Nicholas Andersen, a sea-worn veteran commander. Peter N. Beagle ("Pops") is the Wardog squadron's mechanic. Pops is a former Belkan pilot (actual name, Col. Wolfgang Huckebein) who during the previous war had been assigned the task of dropping a nuclear warhead on a Belkan city. He instead went AWOL and defected to Osean forces, at which time Bartlett found him and arranged a cover story protecting him from reprisal by both Osean and Belkan forces. Captain Allen C. Hamilton serves as the Sand Island Base Adjutant Commander, but in truth, he is a co-conspirator with the Belkans who trained under the antagonist "8492nd Squadron." Hamilton answers to base commander Colonel Orson Perrault, a portly and pompous Osean Air Force veteran who is blinded by Hamilton's influence over his decisions. The 48th President of the Osean Federation is Vincent Harling, a calm-natured pragmatist who struggles to restore the peace at the beginning of the war, but is later captured by the Belkans and kept out of the way as a threat to the Belkans' plans to play off the superpowers against each other.
The story begins with a majority of Sand Island's fighter pilots being killed after they were attacked without warning by a group of unidentified aircraft. Consequently, Blaze, Edge, and Chopper—still trainee pilots—are assigned to Wardog Squadron and placed on active duty. On its second mission, Captain Bartlett is shot down. Although Bartlett bails out, he is not found by the rescue team and is labeled MIA. To make up for this loss, Nagase is made the new Wardog leader, but she refuses and instead allows 'Blaze' to lead. Later, during an air-raid on Sand Island, a pilot in training, Hans Grimm, joins the squadron.
Yuktobania then declares war on Osea, subsequently launching a massive assault on Osean forces. This offense is halted in part by Wardog Squadron, which thwarts several Yuktobanian attacks on the Osean aircraft carrier Kestrel as well as another operation against Sand Island Base. As a result, Yuktobania is forced to abandon its plans to invade Osea, which allows Osea time to prepare a counterattack.
Osea launches a full-scale invasion of the Yuktobanian mainland, intending to quickly capture the capital city of Cinigrad. Throughout the course of the counter-offensive, Wardog Squadron is assigned to fly support missions for the Osean invasion force. As every sortie that Wardog Squadron is a part of somehow turns out to be a victory, the reputation of the squadron increases to the point that their very presence increases the morale of allies while simultaneously terrorizing enemy forces; this, and also in part due to a successful mission executed by Wardog in the northern sea, earns them the nickname "Demons of Razgriz." Despite this, the top Osean military commanders continue to distrust Wardog Squadron because of their lingering suspicions of former squadron leader Captain Bartlett.
During one of Wardog's final missions, Chopper is killed in action while defending an assembly of people who had gathered to hear the Osean Vice President speak from a Yuktobanian air strike. Soon afterward, as the Osean army nears Cinigrad, Wardog is ambushed by a supposedly allied 8492nd aggressor squadron when they are returning home from a mission. It is revealed that the 8492nd is part of a secret Belkan confederacy known as the "Grey Men." This organization seeks vengeance against both Osea and Yuktobania for their role in Belka's defeat in the war back in 1995. The Grey Men singlehandedly instigated this new war by posing as either a Yuktobanian or Osean squadron and attacking the other. They were now using the conflict to exact their revenge against the two superpowers, as a war would drain the resources of both countries. At the same time, Belka profited by selling weapons produced in its own factories (owned by a multinational corporation named Gründer Industries) to Osea and Yuktobania. Over the course of the game, the 8492nd had orchestrated many events that led to the war's escalation and longevity.
After escaping the 8492nd Squadron, Wardog returns to Sand Island, only to see the base commander—already suspicious of Bartlett—accuse Pops, the squadron mechanic, of being a spy. Wardog Squadron is forced to flee Sand Island with Pops and the journalist Genette, but are branded traitors as a result. Captain Snow of the Kestrel, now the only fighter pilot left on the carrier, stages the deaths of the members of Wardog Squadron, who then find refuge aboard the ship. At this point Captain Snow joins Wardog Squadron, with Pops filling a support role from the Kestrel.
The protagonists learn that although the citizens of Osea and Yuktobania are increasily opposed to the war, militaristic leaders and officers seized control of both superpowers' governments with the help of the Belkan Grey Men. Osean President Vincent Harling and Yuktobanian Prime Minister Nikanor, who had peaceful stances with regard to their countries' relationship, were covertly removed from power in coup d'états early in the war. Intelligence acquired by the Kestrel fleet indicates Harling was abducted and imprisoned in Belka. Wardog Squadron and a Marine unit recover Harling from Belkan territory and offer him refuge aboard the Kestrel. He agrees, and he also designates the squadron as a special forces unit under his command; the unofficial unit is renamed "Razgriz Squadron."
Shortly after, it is discovered that the Grey Men have acquired a stockpile of nuclear weapons, which they plan to use against Osea and Yuktobania. Razgriz is sent to locate and incapacitate these weapons. They are aided in their task by an anonymous source from deep within Yuktobania, which eventually reveals itself to be an anti-war resistance organization led by Jack Bartlett. Bartlett had become the first POW of the war, but he had escaped.
The resistance group locates and rescues Yuktobanian Prime Minister Nikanor; once he is flown to Kestrel, he stands alongside President Harling and, through TV and radio, reveals the deception to the world, calling upon all soldiers to cease hostilities. However, the resistance had obtained additional evidence that the Grey Men developed a weapon of mass destruction known as "V2", a MIRV missile capable of destroying many of the major cities in either Osea or Yuktobania. It also lays bare the organization's true purpose: to reunite the partioned Belkan territories. Joined by a coalition of soldiers and pilots from both Osea and Yuktobania who heard Harling and Nikanor's speech, Razgriz Squadron goes off on one last mission to the Gründer Industries headquarters in order to destroy the weapon.
While both factions think the war has ended, the Belkans try a final desperation move. They direct a previously-defunct Osean orbital weapons platform, named "SOLG", to re-enter the atmosphere—to crash into the Osean capital of Oured. However, after its arrival in lower atmosphere, the SOLG's core structures are destroyed by the Razgriz, and the station's descent is stopped before it hits the capital.
Namco first announced it was in development of Ace Combat 5 in the 2002 Tokyo CG festival, in a presentation focusing upon computer graphics. Later, in 2003, Namco launched an official website promoting "Project Aces," originally thought to be a working title for Ace Combat 5. "Project Aces" was later revealed to be the name for the internal Namco development team responsible for the Ace Combat series; AC5 was the first title to directly credit its development to the "Project Aces" team.
To ensure accuracy in the depiction of the game's aircraft, "Project Aces" was given permission by participating aircraft manufacturers to examine in person the planes that were to appear in the game. The visual team also made use of satellite images from the Japan Space Imaging Corporation in the development of the game's environments. Moreover, "Project Aces" incorporated full motion video into the cut scenes of The Unsung War, as opposed to the still images used in the plot sequences of previous titles.
Hiroshi Tanaka, the Namco localization producer for Ace Combat 5, highlights wingman interaction as one of the key distinguishing features between the game and its predecessors. Tanaka says that the wingman interaction feature introduces a "strategic and fun aspect of battle." Tanaka also states that because wingmen play a role in the story, the player can become more involved with the characters and the drama than in Ace Combat 04.
The background music of the game's main campaign mode is primarily orchestral, although the arcade mode features rock music to complement its missions' more frantic pace. The game additionally features three vocal tracks. One is "The Unsung War," a Latin choral piece performed by the Warsaw National Philharmonic Orchestra, that reiterates the "Demon of Razgriz" legend introduced in the game's campaign. Another is "The Journey Home," a recurring song that implies a theme of peace during the campaign. The game also features the licensed track "Blurry" by Puddle of Mudd, which is featured during the game's opening trailer and closing credits.
Officially branded as the Ace Combat Flightstick 2, the Hori Flightstick 2 is a game peripheral specifically designed for Ace Combat 5: The Unsung War. According to Hiroshi Tanaka, Namco and Hori worked together closely to ensure "that the game, the stick, and the controls matched exactly how it should play." Unlike the original Flightstick peripheral designed for Ace Combat 04: Shattered Skies, the Flightstick 2 was released in North America in addition to Japan. In the United States, the accessory was released exclusively as a bundle with Ace Combat 5; only 20,000 bundles were made available in the limited edition offer.
The Flightstick 2 connects to the PS2 through a USB port. Unlike the PS2 DualShock 2 controller, the Flightstick 2 uses a HOTAS, or "hands on throttle and stick" design similar to that used in actual aircraft. The right hand controls the flight stick, which controls the plane's attitude; the left hand controls the throttle. Buttons, D-pads, and rudder controls are placed directly onto either the flight stick or the throttle. Although the Flightstick 2 does not offer force feedback, it does have a vibration feature. Although the Flightstick 2 was targeted specifically for use with Ace Combat 5, not all of the buttons on the peripheral are utilized in the game.
Ace Combat 5 is the only game officially sanctioned for use with the Flightstick 2. In a review of the peripheral, IGN commented that although the Hori Flightstick 2 was "nearly perfect in what it does, [...] at the moment it really only does one thing and that's play Ace Combat 5." However, the Flightstick 2 is also compatible with Ace Combat 04: Shattered Skies and Ace Combat Zero: The Belkan War.
Ace Combat 5: The Unsung War was marked with strong sales, selling over 287,400 copies in Japan and over one million copies in North America, thus making this the most commercially successful Ace Combat title to date . The game was also favorably received by critics. Although reviewers point out that the game is remarkably similar to Ace Combat 04, most also agree that the game's similarity to its predecessor did not detract from its overall quality. According to GameSpot, "this latest installment doesn't do much to change an already-winning formula—but not much was needed to keep this series feeling fresh and exciting."
Overall, critics' reception of the title's gameplay was positive, particularly for the game's intuitive control schemes and large assortment of playable aircraft. The gameplay was also applauded for its "ideal" place between "overtly arcadey rubbish and inaccessible hardcore simulation." Reception of the game's new features, however, was mixed. The game's redesigned "target view" function was decried as "almost broken." Although GameSpy welcomed improvements to the game's radar display, other additions such as wingman commands were seen as "gimmicky" and having little effect on gameplay. The game's arcade mode was described as fun but lacking in features and storyline.
The game's presentation was better received. Various critics praised the way that the game's storyline ties cohesively with the missions, allowing for better and more involving gameplay. GameSpot praised the game for its "captivating storyline." IGN applauded that the game recognizes the player's accomplishments, adding a "sense of worth" to the campaign. Although GameSpy felt that the menu interface was not optimized in terms of usability, it lauded the look of the game's cinematics and briefing screens. Although others believed that the player's responses to wingmen had little effect on gameplay, Game Informer felt that the feature was a "brilliant way to create atmosphere."
The game was acclaimed for its graphics, particularly its improved special and environmental effects and its authentically modeled aircraft. However, critics note that the high level of visual improvement in some areas contrasts with little improvement in others. The game's voice acting received mixed reactions. Although some felt that taken as a whole the radio chatter sets the game's atmosphere and creates a "hectic feel," most critics felt that much of the chatter was contextually inappropriate or annoying. GameSpy compared the voice work in AC5 negatively with that in AC04, feeling that the dialogue seemed "forced" and that sometimes "characters start to blabber just because they can."