There are no second extensions. If you can't file by October 16, you just have to file late.
You might be entitled to an additional extension if you are in a federally declared disaster area. You don't apply for an extension in that case. You get it automatically, based on your zip code. Here's a link to IRS information about tax relief for disaster victims.
https://www.irs.gov/newsroom/tax-relief-in-disaster-situations
