OK, I'll bite. That was the fabric and wood biplane era. There was no scheduled airline service at that time, even airmail service was not begun until 1918 I think. In addition, no aircraft could fly that distance nonstop. People flew the route of course, but the time varied according to the aircraft -- which did not fly very fast -- and the number of stops needed for refueling.
In 1915, planes could barely make 80 mph (trains were as fast, if not faster, more reliable, and carried people with greater comfort), and even the endurance flying record for the US set that year was something over 8 hours, in a special aircraft. It's about 720 miles from Chicago to New York, so a best time for a single engine biplane at 80 mph, with refueling, would probably be no better than about 10 hours in a perfect situation. However, with pilot fatigue (that endurance issue again) and the difficulty of flying at night (no instruments, star navigation at best), I would suspect it was either done in two legs with an overnight stay somewhere, or in about 10-12 hours of flying.
That's a guess.
Bear in mind that as late as 1916 there were only a handful of trained pilots, and no commercial service. The entire US Military had only 24 trained pilots. Planes weren't used for transportation, they were mostly novelty items like hot air balloons or blimps are now.