I’ve recently took a snapshot quite long time ago for my images. When i tried to delete the snapshot, it prompt me snapshot snap-idxxxx is currently in used by ami-xxxx.
Reason
The main reason you’re unable to delete the snapshot because it is still register with the AMI.
Solution
1. From the left panel, select the AMI then you’ll see a AMI record.
2. Select the AIM, then click the actions button and select deregister.
3. Go back to your snapshoot from the left menu and delete again. You should able to delete it.
Amazon – Error Deleting Snapshots