Airship Down

Airship Down is an Institute quest in Fallout 4. In this quest, the Sole Survivor, along with an army of synths, storms Boston Airport in an attempt to cripple the Brotherhood of Steel. This is done by hacking Liberty Prime into targeting the Brotherhood of Steel as Chinese Communists. Liberty Prime then destroys The Prydwen via his dual eye lasers.

Detailed walkthrough
Doctor Li greets you and then leaves to Rosalind Orman to explain the details of this quest. She informs you that the target is the base of the Brotherhood of Steel operations in the Commonwealth - the Boston Airport. It is shielded by a electromagnetic shield that makes it impossible for the Institute to teleport troops into the base. The plan is that you will take down the field by infiltrating a poorly-guarded part of the airport, and from there work your way to the generators and destroy them. For each generator that is destroyed, the Institute will teleport some synths into the base. She gives you a couple of Institute Beacon markers, which you can then use to call in extra synths to the point where a marker is placed.

After that, you will go to the main target - a huge robot named Liberty Prime. Doctor Li explains that it is an old weapon, and also tells you about her role in making it operational. Working with Liberty Prime has given her good knowledge on how it works, which will now be used to manipulate it. Rosalind enthusiastically explains that a synth has been programmed with a computer virus and will transfer it to Liberty Prime, making it believe that the Brotherhood airship Prydwen is a communist vehicle. Your job is to bring that synth safely to Liberty Prime.

You relay from the Institute to the airfield and fight your way to the generators, and then to Liberty Prime. Climb up to the head of the robot so that the hacker synth can begin uploading the virus. Defend the hacker against a massive assault from both the air and ground. Before finishing the upload, Elder Maxson attacks via a vertibird. If the vertibird is destroyed, he will fight on the ground. This gives the player the opportunity to obtain his Elder power armor and his unique weapon: Final Judgment. When the upload is complete, Liberty Prime will announce that it will attack the "communist" vessel, and fires its eye laser at the ship. As the ship begins to fall, you will be teleported a short distance away to observe the firey wreckage.

The quest completes, and the next quest starts.

Bugs

 * There is a bug in which Doctor Watson doesn't explain anything.
 * It can happen that the hacker synth will not spawn to reprogram Liberty Prime and one will be stuck to reach Liberty Prime.
 * Fusion core will not spawn in the generator and will still run even though the player character previously took it in the past.
 * Only current fix for the fusion core bug and the synth bug is to complete it via the console. To complete the quest type into the console "completequest Inst307".
 * Elder Maxson disappears after player character leaves area.