You can now use Recycle Bin for Amazon Machine Images (AMIs) to recover from accidental deletions to meet your business continuity needs. Previously, you could not recover AMIs if you accidentally deregistered them. With Recycle Bin, you can specify a retention time period and recover a deregistered AMI if needed, before the expiration of the retention period. A recovered AMI would retain its attributes such as tags, permissions, and encryption status, which it had prior to deletion, and can be used immediately for launches. AMIs that are not recovered from the Recycle Bin are permanently deleted upon expiration of the retention time.
Source:: Amazon AWS