There are a whole slew of new achievements to be found in the zombie map ‘Mob of the dead’ of Black Ops 2. One of these achievements is called Making the Rounds. This achievement can only be unlocked after you have finished construction of the airplane.
When you use the plane it crash-lands onto the golden gate bridge where there are a bunch of zombies, a pack-a-punch machine and a set of electric chairs. You cannot go anywhere from this location except back to the island via use of the electric chairs.
If you want to get the achievement, you need to go to the bridge and back a total of three times. To use the plane a second time you need to collect gas cans around the map. The cans can be found in the same locations where you originally find the components of the construct.
Remember that you need to go back to the prison after the third trip to unlock the achievement!
You can also get the GG Bridge achievement here which simply requires you to survive a round after round 15 on the bridge.