Airdrop

    void SpawnAirdrop()
    {
        RemoveAirdrop();
        int randomIndex = Math.RandomInt(0, dropLocations.Count());
        currentDropPos = dropLocations[randomIndex];
        currentCityName = cityNames[randomIndex];
        dropContainer = GetGame().CreateObject("Land_Wreck_offroad02_aban1", currentDropPos, false, true);

        if (dropContainer)
        {
            SpawnRandomLoot();
        }

        spawnedZombies.Clear();
        array<string> militaryZombies = { "ZmbM_SoldierNormal" };
        for (int i = 0; i < ZOMBIE_COUNT; i++)
        {
            vector zombiePos = currentDropPos;
            zombiePos[0] = zombiePos[0] + Math.RandomFloat(-5, 5);
            zombiePos[2] = zombiePos[2] + Math.RandomFloat(-5, 5);
            Object zombie = GetGame().CreateObject(militaryZombies.GetRandomElement(), zombiePos, false, true);
            spawnedZombies.Insert(zombie);
        }
        GetGame().ChatPlayer("Airdrop érkezett " + currentCityName + " (" + currentDropPos[0] + ", " + currentDropPos[2] + ")");
    }

I'm asking for help because no matter what I put in the container, it all sinks underground.

You need to place the container on the ground. 
Example:

dropContainer.PlaceOnSurface();

dropContainer.SetPosition(dropContainer.GetPosition()); //Re Place On Surface at current pos

dropContainer.SetDirection(dropContainer.GetDirection());

dropContainer.SetOrientation(dropContainer.GetOrientation());