As of Tuesday, search aircraft had flown 45,700 miles looking for the missing de Havilland Beaver. There was still no sign of the plane, the Park Service said.
Pilot Marco Alletto, 47, is missing along with passengers Mason McLeod, 26, Neal Spradlin, 28, and Seth Spradlin, 20.
Meanwhile, the Park Service is looking for clues that could help narrow the search area.
Anyone who heard a signal from the plane's emergency locator transmitter on 121.5 MHz after Aug. 21 in the Katmai National Park area is asked to call 907-246-3305.
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