Grand Theft Auto: San Andreas Walkthrough

While in the studio with Madd Dogg, CJ gets interrupted by Toreno, who sends him on a mission to sneak aboard a carrier ship for a secret mission.

Once you take control, take the speedboat and head toward the carrier, marked by a yellow blip on the radar. As you get closer, hop out of the boat and swim in through the back with your knife and silenced pistol.
Taking control again, you'll want to stay as stealthy as possible. Stay crouched and sneak up on the engineer and armed guard. Use your pistol to kill them both.
Each of the guards on the boat will be marked by a red blip on your radar.
Head up the stairwell one level and continue straight ahead, taking out the guard in the green room. If you continue straight through there, you'll see a tiny control room with a red marker, allowing you to disable to SAM turret and ease your escape.
Once you've disabled the turret, turn around and head down the long hangar to the other end of the carrier. Take out the 3 guards at the end of the row.
Board one of the jet harriers. The government will send 3 additional jets to take you down, which will be marked with 3 red blips on your radar. Use your homing missiles to shoot them down.
Once all 3 have been destroyed, you'll need to destroy 4 additional enemy spy ships in nearby waters. They'll be marked with yellow blips on your radar.
Once you've used your missiles to successfully take them out, you need to pilot the Hydra jet back to the abandoned airstrip, marked by a yellow blip on your radar. Land in the designated area, noted by the red marker.
You'll be prompted to taxi the jet into the hangar. Do so and you've passed.