Biffle, his wife and his two children, along with three others, died in the Dec. 18 crash, which remains under investigation by the NTSB.
Over 40 search warrants have been issued, NC authorities say, focusing on a married couple who allegedly knew Biffle and his wife Cristina.
The Dutton estates filed the lawsuits earlier this week, each seeking $15 million in damages.
A familiar name may be introduced at the 2031 Daytona 500 when Keelan Harvick will be old enough to enter the race his father won 24 years ago.
Tyler Reddick won the Daytona 500 in a car owned by Michael Jordan when Chase Elliott crashed as he and Reddick were battling for the win.
Retired NASCAR driver Greg Biffle was not flying his own jet when it crashed last month.