On the same day the death toll from a floatplane collision in southeast Alaska rose to six people, federal investigators launched what's expected to be a week-long investigation in the popular tourist area.
The U.S. Coast Guard announced search crews found the bodies of two missing people on Tuesday night, hours after the National Transportation Safety Board arrived to figure out how a sightseeing excursion into Misty Fjords National Monument ended in tragedy.
Investigators will gather evidence in the coming days, NTSB board member Jennifer Homendy said at a press conference, but will not determine the cause of the crash while in Ketchikan.
Teams will request and analyze the routes of each plane, the training and qualifications of each pilot and Federal Aviation Administration oversight of the operators. The safety board also plans to interview the surviving pilot and recover wreckage.
Neither plane had cockpit voice recorders installed, Homendy said, and regulations did not require them to do so. Two pilots guided a collective 14 passengers from the same cruise ship on tours.
Here's what we know so far:
Where did the planes collide?
The planes crashed about eight miles from Ketchikan, near George Inlet. They met at an altitude between 3,200 and 3,300 feet, Homendy said, as both flew southwest toward Ketchikan.
Preliminary data shows the plane operated by Taquan Air descended from about 3,800 feet traveling at 149 mph, while the smaller plane owned by Mountain Air Service of Ketchikan was maintaining an altitude of 3,300 feet at 125 mph.
But assumptions cannot be made from the speed and altitude alone, Homendy said.
"It takes some significant work to really understand how the two really came together," she said.
Is the site of the crash a controlled space?
No, said lead investigator Aaron Sauer. The area is not controlled, he explained, so the pilots were not required to talk with a staff at a communications tower.
In controlled airspaces, air traffic controllers coordinate the movement of planes on the ground and in the air so they keep a safe distance.
Boeing engine failure: Passengers hear 'loud bang' as plane's engine shuts down, flight diverted
Airplane bird crashes: Planes strike birds more than 40 times a day, FAA data show
Investigators will determine whether pilots filed flight plans with their companies or the FAA. They have requested flight track data from the latter.
Who is injured or dead?
Ten people, all Americans, were injured. Hospital staff released three of them Tuesday and listed the rest in fair or good condition, spokeswoman Marty West said.
The last two bodies found Tuesday were near the the crash site of the smaller plane involved in the collision, Coast Guard Lt. Brian Dykens said.
Earlier in the day, Dykens said three of the dead were among the five aboard that same plane. Princess Cruises identified them as two passengers and a pilot.
The Alaska State Troopers identified the six deceased as Randy Sullivan, 46, from Ketchikan; Simon Bodie, 56, from Tempe, Australia; Cassandra Webb, 62, from St. Louis; Ryan Wilk, 39, from Utah; Louis Botha, 46, from San Diego; and Elsa Wilk, 37, from Richmond, British Columbia, Canada.
Authorities listed Sullivan as a pilot. He was owner and pilot of Mountain Air, the operator of the smaller plane in the collision, according to the company's website.
Where are the remains of the planes?
The smaller plane was partially submerged in the shore of George Inlet after the single-engine plane overturned and and hit trees before crashing, Dykens said. The larger plane carrying 11 people landed in the water and sank.
While the smaller aircraft's floats landed near shore, the plane's tail and section of the fuselage crashed 900 feet away. It seems to have broken apart in midair, said Jerry Kiffer, duty incident commander of the Ketchikan Volunteer Rescue Squad.
Contributing: The Associated Press
This article originally appeared on USA TODAY: How did it happen? NTSB begins probe of midair collision of Alaska floatplanes that killed 6 people