The 35-year-old Cronulla Sharks champion was en route to Sin City for the Cowboys vs Knights and Bulldogs vs Dragons matches scheduled for Sunday.
Townsend's mid-flight medical emergency comes as players prepare for the start of the new NRL season.

NRL premiership winner Chad Townsend required medical treatment during a flight to Las Vegas ahead of the NRL season opener, describing the ordeal as 'scary'.
The 35-year-old Cronulla Sharks champion was en route to Sin City for the Cowboys vs Knights and Bulldogs vs Dragons matches scheduled for Sunday.
Townsend's mid-flight medical emergency comes as players prepare for the start of the new NRL season.