)and San Francisco (Marina Field ) began on September 8, 1920, over a route laid out in July and August by Eddie Rickenbacker and Bert Acosta who had helped pilot the first experimental through flight carrying about 100 letters which landed at Durant Field located at 82nd Ave and E. 14th St. in East Oakland.The transcontinental mails were originally flown only during daylight hours while being entrained at night, although on February 22, 1921, a nighttime leg on this route (Omaha to Chicago) was flown for the first time with Jack Knight as the pilot.