- This article is about an in-game mission. For the in-universe event, see Operation Emerald.
- "Are you listening to me?! This is war here! The freight terminal's getting shot at! Dammit! This is a civilian airport!"
- ― Apito control tower
Chain Reaction is the 11th campaign mission of Ace Combat 5: The Unsung War. It plays after Blind Spot if the player said "Yes" to Chopper's question about a song at the start of that mission. Alternatively, saying "No" will play Reprisal instead.
Yuktobanian aircraft have suddenly been detected on radar southwest of Oured. They are flying in the direction of Apito International Airport, located in the area between Oured Bay and the capital. Apito International is a civilian airport. The enemy's intentions are unknown. Passengers and personnel are currently being evacuated, but the sudden appearance of the enemy has plunged the airport into chaos. Intercept and engage the invading enemy formation and protect Apito International Airport.
The mission's first objective is to destroy all enemy fighters.
After all enemy fighters are destroyed, the transports at the airport become TGTs, and several TGT ground units spawn. In addition, several waves of TGT fighters arrive as reinforcements. Destroying all TGTs ends the mission.
The enemy forces that tried to capture Apito International Airport have been destroyed. Hopefully, we'll find out how they managed to infiltrate the airport after we complete our investigation. Additionally, the effects of the chemical attack on the college town of Bana are currently subsiding, thanks to the neutralising agent that was spread. The group that carried out the chemical attack are all but confirmed to be a Yuktobanian special forces commando unit. They were planning to link up with the main force at the airport, but they aborted their plan and slipped away upon hearing that their main force was defeated. The Yuktobanians have defiled our soil. Worse, they tried to destroy a civilian airport. We've got to defeat them, no matter the cost. We'll be sending you back to the front lines of the Yuktobanian mainland. If you all really are innocent, then I hope you can prove it out there on the battlefield.
- Multiple airline corporations are displayed in the mission, all flying 747-400s. In the initial stage, two Osea West airliners are in the sky, and they will fly erratic patterns circling the airport. On the ground, multiple Osea West, Air Ixiom, and Air Erusea aircraft can also be identified.