What year did the Post Office begin
flying the air mail on a scheduled basis?

Start of Scheduled Airmail Service, 1918

The Post Office Department began scheduled airmail service between New York and Washington, D.C., on May 15, 1918 — an important date in commercial aviation

Explanation:

as general terms,  indian territory,  the indian territories, or  indian country  describe an evolving land area set aside by the  united states government  for the relocation of  native americans  who held  aboriginal title  to their land. in general, the tribes ceded land they occupied in exchange for  land grants  in 1803. the concept of an indian territory was an outcome of the 18th- and 19th-century policy of  indian removal. after the  civil war(1861–1865), the policy of the government was one of  assimilation.

the government paid religious orders to provide basic education to native american children on reservations. in the late 19th and early 20th centuries, the bureau of indian affairs (bia) founded additional boarding schools based on the assimilation model of the off-reservation carlisle indian industrial school.