The U.S. Coast Guard has also confirmed the identity of the Canadian who died in the crash as 37-year-old Elsa Wilk of Richmond.
The planes were carrying passengers from a cruise ship which departed from Vancouver on Saturday.
Five others were killed in the crash including four Americans and one Australian.
Authorities say the collision occurred at 1:08pm on Monday, local time, in George Inlet some eight nautical miles from the town of Ketchikan, where cruise ships often stop.
The search operation is being led by the US Coast Guard.
An Otter floatplane with 11 people onboard was returning from a Misty Fjords tour while a second Beaver floatplane carrying five people was on an independent tour.
"All of us at Princess Cruises are deeply saddened by this tragic news and we are extending our full support to the investigating authorities as well as the travelling companions of the guests involved", company spokesman Brian O'Connor said in a statement.
A team of federal accident investigators from the National Transportation Safety Board is expected to arrive in Alaska Tuesday to begin work on piecing together what happened.
According to his mother, Sullivan had been a pilot with Mountain Air since 2012, flying tour groups over the rugged wilderness of Alaska's Inside Passage, a popular cruise ship route. One person was critical and three were in a serious condition, it cited a medic at a local hospital as saying.
Ten people were rescued and are receiving medical care, the extent of their injuries are unknown.
Eleven people were inside Taquan's single-engine de Havilland Otter DHC-3 when it went down as it returned from Misty Fjords National Monument, which is part of the Tongass National Forest, the nation's largest.
Officials said the crash happened at George Inlet near the city of Ketchikan, and involved two small float planes.
Both aircraft plunged into waters below, where they are submerged, a source familiar with the situation told CBS News.
Princess Cruises in its release said two passengers and the pilot were among those killed in this plane. In Ketchikan Medical Center, three are in good condition and three have been discharged.
The NTSB later determined that pilot error and lack of a formal safety programme were behind the crash.
"Our community is heartbroken over this tragedy and its devastating impacts on so many families", Ketchikan Gateway Borough Mayor David Landis said in a statement.