Alps Air Corridor (HARD)

 is a more challenging version of the Online Co-Op Mission Alps Air Corridor, featured in Ace Combat Infinity. It takes place over the, where the players are working together to assault a fortress in the region.

In-Game Description
''Attack the enemy fortress located in the Alps Mountains. Construction on the fortress started during the Second World War, with secret expansions continuing through the Cold War. The vast underground facility caught the attention of the enemy, and resulted in further construction of a ground facility to provide protection from bombing. Continuing our advance while leaving this play creates the risk of a surprise attack. Due to its subterranean structure and the nature of terrain, a guerrilla style response from the enemy expected. Remain alert at all times.''

Objectives
The mission itself bears similarity to the assault against Bartolomeo Fortress. Alpha team begins right where Garuda team started if they chose to assist Warlock Separate Battalion first, while Bravo team begins right where Garuda team started if they chose to assist Quox Armored Battalion first. Alpha team can assist the UNF ground units advancing from the west side of the fortress, while Bravo team assist the team advancing from the east side. Both sides have mainly ground targets with one "SP" ground target in each checkpoint. Air enemies are random. Players may encounter Su-27s and MiG-29s in the sky which are first gathered on the location where Snake Pit used to be: the middle point between the two enemy lines, or SP F-15Es and Typhoons flying in pairs which begin above each checkpoint.

After the emergency mission update, the mission again bears resemblance to the second phase of the attack against Bartolomeo Fortress. The enemies are concentrated around the highest mount in the area. And like the Bartolomeo Fortress, the ground units here have formidable anti aircraft capability. In the sky, mixed squadrons of F-14Ds, JAS-39Cs, and SP F-15S/MTDs will appear after the mission update. Players may also find SP Tu-95s flying at high altitude, but they are not required to get an S-rank for the mission as the enemies on the ground and the jet fighters present at the lower altitude are already sufficient to get an S-rank.

The mission ends after all hostiles in the area are destroyed or the timer runs down to zero.

E or D Rank
''Enemy losses were limited to forces above ground, with the subterranean facility and the forces stationed there remaining almost unharmed. Creating a defensive perimeter around the fortress is going to require a more serious commitment of troops on our part.''

C or B Rank
''While some enemy forces do remain in the fortress, their attack capabilities have been weakened. Command HQ is considering whether or not another attack is required in order to secure the rear of our forces.''

A Rank
''Our air assault has completely shutdown all enemy activity in the vicinity of the fortress. Although the status of the deepest areas remains unknown, there is surely nothing left that can threaten our forces.''

S Rank
''Your rapid and precise air attack has been successful, with recon reporting zero enemy activity in the vicinity of the fortress or in the subterranean sections. It will be a long time before the fortress is functional again.''