The crash in Ohio killed all three people on board, while both crew members were rescued from the plane that went into the Mississippi. Both planes were twin-engine Falcon 20 turbojets operated by Grand Aire Inc.
A flag outside the company's offices at Toledo Express Airport flew at half-staff Wednesday. An employee said no one from the company was available to comment.
The causes of Tuesday's crashes had not been determined, although one plane reportedly was low on fuel. Police and the FBI in St. Louis said they were taking precautions but had no reason to believe the crash there was a result of terrorism.
``Because the country is on an orange alert and because Mississippi River bridges have been listed as possible terrorism targets, we are handling this matter with extreme caution,'' Mayor Francis Slay said.
Officials have said in the past that Mississippi River bridges and the Gateway Arch in downtown St. Louis, near the crash site, were potential terrorism targets.
Investigators from the National Transportation Safety Board began work at the Ohio crash site Wednesday and a board investigator was sent to St. Louis.
Three other Dassault Aviation Falcon 20s owned or operated by Grand Aire have crashed since 2000, according to NTSB records. No one was killed in those crashes, but the company did have a fatal crash last year involving another type of plane.
The French-built Falcon 20s are reliable and safe, said Dick Williams, president of Aviation Data Source, a Denver-based aviation group. ``There's nothing tricky about flying them,'' he said.
As for two of them belonging to one company crashing on the same day, Williams said: ``You can't calculate the odds. That's just not going to happen.''
One of the Grand Aire planes crashed in flames in a remote area of a nature preserve Tuesday afternoon as it approached the Toledo airport. It was on its way from Traverse City, Mich., Lucas County Sheriff James Telb said.
Deputies and park rangers found the wreckage by following a horse trail toward smoke in the 3,500-acre Oak Openings Preserve MetroPark, a mile southwest of the airport.
The victims were Grand Aire employees Dave Davenport, 40, of Elmore, Ohio; Will Forshay, 37, of Maumee, Ohio; and Wallis Bouldin, 34, of Louisville, Ky., the State Highway Patrol said. It was not yet clear who was in control of the plane.
All three were experienced fliers, said Tahir Cheema, Grand Aire's owner and president. He would not comment further Tuesday.
About five hours later, a second Grand Aire Falcon 20 crashed into the Mississippi River just north of downtown St. Louis.
That plane was en route to St. Louis' Lambert Airport from Del Rio, Texas, said Federal Aviation Administration spokeswoman Elizabeth Isham Cory.
The St. Louis Post-Dispatch quoted an FAA source as saying that while the plane was circling for a second attempt at landing at Lambert, the crew radioed that the plane was critically low on fuel.
The pilot and co-pilot were rescued from the water. ``They were both conscious and talking,'' St. Louis Fire Department spokesman Steve Reynolds said.
The men were identified as Saleem Iqbal, 34, and Mohammed Saleh, 44. Hospital officials said Iqbal was in serious condition Wednesday and Saleh was in fair condition.
On July 18, a twin-engine Piper PA-60 owned by Grand Aire plane crashed while attempting to land in fog at Columbus, Ind. The pilot was killed.
