- This article is about an in-game mission. For the in-universe event, see Operation Early Bird.
Lifeline is the fifth campaign mission of Ace Combat 04: Shattered Skies.
Comberth Harbor, home of the Aegir Fleet, is completely dependent on a single petrochemical complex for its fuel supply. The complex consists of a land based oil refinery/storage facility, and an offshore oil-drilling platform. Your mission is to go out and destroy, or at least damage, these sites. Our objective is to reduce production output of this complex to 20% or less. By cutting off the port's fuel supply, we will delay and disrupt the combat deployment of the Aegir fleet.
This time, instead of destroying designated targets, the main objective is to destroy as many enemy units as possible within ten minutes. The minimum score necessary for mission completion will earn the player a "C" rank. As most of the targets are ground-based, a bomber/attacker aircraft equipped with a SP weapon that generates splash damage will work well here. It does not matter which of the facility's main sites is attacked first.
Once both the oil rigs and refinery are destroyed, and ten minutes have elapsed, AWACS SkyEye informs the fighters that the Erusians' fearsome Yellow Squadron has arrived, and orders them to disengage and return to base. The Yellows cannot be shot down, so engaging them is futile. The mission is completed once the player crosses the dotted white Return Line at the bottom of the map.
An S rank is achieved in this mission by scoring 4,000+ points within the 10-minute time limit. The other three rankings' thresholds (in ascending order) are as follows:
- C: 2,000+ points
- B: 2,500+ points
- A: 3,000+ points
Main article: Ace Combat 04: Shattered Skies/Aces
The enemy lost 5 million barrels of reserves and the ability to process 250,000 barrels of crude oil daily. The Aegir Fleet is effectively immobilized and no longer a threat. Unfortunately, our losses were high as well. We now rely on your skills more than ever to compensate for our losses.
- This mission is the first to feature Yellow Squadron outside of cutscenes.
- Following the release of Ace Combat 04, some fans reported that they were able to either hit or shoot down a Yellow during this mission, widely believed to be impossible. The game's director, Hiroyuki Ichiyanagi, expressed his surprise upon reading such claims, realizing that they hadn't made the Yellows as invincible as they had hoped.