The Model C two-place training seaplane was the first "all Boeing" design and the company's first financial success. Following its first flight on Nov. 15, 1916, the U.S. Navy bought 51 of the trainers, and the U.S. Army bought two landplane versions with side-by-side seating, designated the EA.
The final Model C, outfitted as a mail plane, was built for William Boeing and called the C-700 (the last Navy plane had been Navy serial number 699). The company was facing difficulties due to the cancellation of military contracts after World War I. The airmail market was developing and a delivery contract with the government would provide a good stream of income for the company.
On March 3, 1919, Boeing and lead test pilot Eddie Hubbard flew the C-700 from Seattle to Vancouver, British Columbia. On the return flight they carried a bag of 60 letters to Seattle, recording North America’s first international airmail flight.
Here is Boeing’s recollection of that flight: