Not a "twotter" Aircraft proposed is a Cessna Caravan.
15 passengers would be a good load in a Caravan!
"The company estimates each flight would be able to carry 15 passengers, each paying about $300 for a one-way ticket."
"Sydney Seaplanes would use a 15-passenger de Havilland Twin Otter seaplane like the one pictured."
You wouldn't think there were too many spare Otters
floating around!