There were a lot of people trying to use the airport as an evacuation zone in Gray Zone Warfare. It was chaos when things happened, but some important information was left behind. Handshake wants you to find that information, and he knows it's in a purple suitcase.
Final Control Task Guide – Gray Zone Warfare
The Final Check Out mission is another personal affair with Handshake. He has a client who wants to know what happened to his wife after everything happened, but you have to find her luggage to do so. Handshake has a vague idea where you can see the purple suitcase in Gray Zone Warfare, and finding its exact location is up to you, along with bringing details back to Base Camp.
You’ll find the purple suitcase on the eastern side of Pha Lang Airfield. The suitcase should be sitting next to a large pile of other bags under a covered area. Expect this location to be heavily guarded, with multiple NPCs patrolling the area. You can also expect to encounter a handful of GZW players wandering around, likely completing their missions.
Be careful when approaching Pha Lang Airfield as you walk through the fields. A handful of NPCs patrol outside the airport walls, making it easy to get shot if you go straight through this area. The best thing you can do is use a weapon with a decent scope and a silencer to make it harder to alert the entire location to your arrival.