It's because-" Just then a big multi-engined plane came over, drowning out his words.
"The Hohokam Dig"
Theodore Pratt
In diesel-engined airplanes the size of the engine could be reduced by 25 percent by feeding oxygen into the intake air during the takeoff.
"The First Airplane Diesel Engine: Packard Model DR-980 of 1928"
Robert B. Meyer
There was a light head wind, but not enough to deter any of the powerfully engined craft.
"The Girl Aviators' Motor Butterfly"
Margaret Burnham