(Denver-AP) -- Most of the nation's fleet of heavy firefighting air tankers are allowed to return to duty Saturday, two days after the second deadly crash since June involving one of the former warplanes.

Still grounded pending results of federal investigations are nine planes of the same types as those that crashed in June in California and on Thursday near Lyons, killing a total of five crew members.

The government yesterday ordered a 24-hour stand-down of 32 other tankers to allow for inspections of planes and to give crews a rest.

Relatives have identified the victims of Thursday's crash as 39-year-old Rick Schwartz of Montana and 56-year-old Milt Stollak of California. Larimer County officials won't release the names until positive identification is made.

It's unclear who was flying the 57-year-old PB4Y2 Privateer when it came apart in the air on Thursday.

The National Transportation Safety Board and U-S Forest Service are investigating.

There are 32 tankers available to fire managers again Saturday, but National Interagency Fire Center officials say some of them might not return to service immediately to allow for more thorough inspections.