In case when you lost private keys from AWS EC2 instances you will need a way to restore it. Unfortunately you can’t just change instance private key in AWS Management Console. The easiest way to do it which I found is through Amazon Machine Image (AMI). Basically all you need to do is recreate you instance from AMI and set new private key to it. Below I describe required steps to do it.
Steps to change EC2 key pair
1) Shut down your instance
2) Create AMI for that instance and provide some meaningful name for them
3) Go to “Images > AMIs”. You need to launch instance with the same type from created AMI
4) On the last step of launching you will be asked about key pair. So it’s time to create/chose private key which you want to use with this instance
5) After that you need go to “Network & Security > Elastic IPs” and disassociate ip from old instance and associate with created instance
6) And finally terminate old instance
Well, now you have instance with you new private key and you can connect to it thought ssh.