Level 13: Unfriendly Skies is the thirteenth level of Shadow Warrior Classic.
- There is a switch next to the pachinko machines on the north. Press the switch and jump on top of the pachinko machines and duck into the opening over the machine to the far side of the switch and grab the missiles inside.
- After you grab the red key card from the airplane past the pachinko parlor, go to the elevator that uses the red access card and call for it. Send the elevator back down and go back to the room that has the 3 phones, candy machine, pop machine and 3 pachinko machines. Look above the candy machine and you'll notice a hatch has been opened. Jump up to the hatch and walk into the duct until you come to the grill. Shoot it out and pop out the other side and collect the caltrops, portable medkit, Riot Gun, and grenade shells.
- Go back to the red access elevator and ride it down to the lower level. Walk straight ahead to the west and up the spiral staircase to Impulse Gifts. Use the cash register once you are in the gift shop and a secret area will open up in the wall straight across from you. Jump over inside of it and grab the fortune cookie.
- Walk back down the spiral stairs from the gift shop and then turn to the south and walk into the short hallway. Turn to your right heading west and then left into the baggage claim carousel. Go into the conveyor room and proceed to where you see the Nin-Nin Airline banner on the north wall. Turn around and face the conveyor and you'll see a baggage shoot in front of you. Jump into the baggage shoot and walk up inside of it until you come to an open area that is guarded by Baby Rippers. Turn to your right facing south and you'll see the baggage compactor and a switch in front of it. Hit the switch and a secret area will open up inside the baggage compactor to the left that holds a Grenade Launcher and a portable medkit. Once you jump into the baggage compactor, It will start to compact, so duck into the secret area quickly before it closes on you. Time your exit from the compactor when it stops crushing after 4 cycles.
- After finding the last secret area, walk back down the way you came into the baggage conveyor into the baggage claim again. As you walk back to the exit, you'll see an air grill to the right of the hallway. Shoot out the grill and jump into it from the edge of the baggage carousel. Walk through the duct and shoot out the grill on the other side and jump out. Now turn to your right, heading south, and follow the path into Blue's Brews. Once inside of the bar, there is a banner on the west wall up a little ways from the ground. Jump up and push the banner and a secret area will open up to the right of the banner revealing a room with a Railgun spinning mid-air in a Ying-Yang symbol.
- Go into the yellow access door into the control room where you get the blue access card. As you enter the control room, you'll see a pop machine on the west side of the room. Jump on top of the pop machine and turn back facing into the room. You'll see a red button on the side of the radar panel in the center of the room. Shoot the button and turn around on the pop machine and duck into the secret area that has been opened and grab the Ripper Heart inside.
- (Secret level entrance) The final secret area in this level takes you to the 2nd secret level. Go back to the red access elevator and ride it to the main level. Walk out and then hit the call switch to send it back down and quickly walk into the elevator before the door closes so that you are actually on top of the elevator. Turn and face north and jump up and hit the switch to send the elevator back up. Now turn around to the south and walk into the duct and grab the nuclear missile. Just past the missile is the entrance to the secret level Auto Maul.
- The plane that crashed in the previous level is seen in the airport.