Hi.
If someone kills heli on my server, the crates are not spawning. There is no permission helicontrol.nodrop added to any groups, so I really don't know where is the issue. 
Thanks for any replies.

You should read again...

Permission:
helicontrol.dropcrates - Whoever has this permission, when they call a heli, that heli will spawn crates on death.

Config:
Loot - Max Crates to drop (default 4) - The amount of crates to drop when the Helicopter is destroyed.
Misc - Prevent crates from spawning when forcefully killing helicopter (default true) - If set to false, /killheli will still let the helicopter drop it's loot crates.