The surviving pilot of a fatal mid-air crash between seaplanes carrying cruise ship passengers estimates his aircraft hit the water five seconds after they collided, according to the preliminary report that has American investigators calling for greater safety measures.

The National Transportation Safety Board’s preliminary report into the May 13th crash near Ketchikan, Alaska, where six people died, describes the crash as "one in a string of recent accidents involving for-hire aircraft" and does not discuss probable cause, but does report information investigators have gathered.

Two of the passengers - Ryan and Elsa Wilk - were Metro Vancouver residents who, like the other passengers, had travelled to the area aboard a Princess Cruise trip out of Vancouver.

The NTSB report notes the weather was clear for flying and both the De Havilland DHC-2 Beaver operated by Mountain Air and the De Havilland DHC-3 Otter operated by Taquan Air had been flying round-trip sight-seeing tours from Ketchikan to the popular Misty Fjords National Monument 30 nautical miles (55 kilometres) away.

Investigators say the Preliminary flight track data found the Otter was flying southwest and gradually descending from 3,700 feet as it crossed into the George Inlet, while the Beaver was travelling west-southwest at 3,350 feet -- where the two aircraft collided.

The surviving pilot, flying the Otter, told investigators he hadn’t seen any aircraft on hits Automatic Dependent Surveillance Broadcast display, and "Just prior to the collision, he saw a flash from his left side, and experienced a large, loud impact…he was able to maintain some control and flare the airplane prior to impact. The pilot estimated that the airplane impacted the water about five seconds after the collision."

Remarkably, of the 10 people on board that aircraft, all were evacuated with various injuries but only one died.

But the other aircraft broke into so many pieces; the debris field was 600 metres long and 300 metres wide. The pilot, 46 year-old Randy Sullivan, and all four passengers on board died.

In a press release summarizing the preliminary report, the NTSB notes full investigations into major crashes involving fatalities typically take between 12 and 24 months, but in the meantime, the agency is calling for greater safety measures.

On its website it notes small aircraft operate under Part 135 of FAA regulations, which "doesn’t require air medical service, air taxi, charter, or on-demand flights to meet the same safety requirements as commercial airlines."

"While these tragic accidents are still under investigation, and no findings or causes have been determined, each crash underscores the urgency of improving the safety of charter flights by implementing existing NTSB safety recommendations," said NTSB Chairman Robert Sumwalt.

The release goes on to say, "The NTSB’s safety recommendations call on Part 135 operators to implement safety management systems, record and analyze flight data, and ensure pilots receive controlled-flight-into-terrain avoidance training."