An economic downturn during the early 1920s dampened tractor sales; price-cutting to stimulate demand sparked a price war in the tractor industry (called the tractor war).
While the number of destinations served by both airlines increased from two to six, there was no price war and both companies continued to make a profit.
By then, not only had an economic recession and resulting tractor price war damaged such companies' finances, but also, the tractor market was evolving.