572 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



all factors of expense, including salary loss, and under three classifi- 

 cations. For the middle case, a salary of $3,500 per year, it appears to 

 be economical to travel by air if the distance involved is 750 miles or 

 greater, and under the assumption that the alternative of rail travel 

 would be carried out at night to cut down the salary loss while travel- 

 ing to nothing or to a minimum. If travel were to be carried out in 

 the daytime by either means of transportation, the lines representing 

 air and rail travel cross at about 200 miles for all salary brackets. 



Under figure 2 {B) a, few statistics are shown. Reduction in 

 passenger fare from 12 cents a mile to 5.7 cents has brought this item 

 to a point where, from figure 2 (A), it appears reasonable travel 

 economy is effected. The tendency for passenger-load factor to 

 stabilize at 60 percent requires some comment as, offhand, it might be 

 considered that a larger amount would be necessary or at least de- 

 sirable. However, it should be realized that in order to attain this 

 average, there must, of necessity, be many trips which are 100 percent 

 filled. It is also evident that at 100 percent load factor, it would be 

 likely that in many cases passengers would be turned away because of 

 lack of capacity. Furthermore, such a lack of capacity would imply 

 failure on the part of the operators to render a service which can 

 reasonably be expected by the public. It appears that the tendency 

 to stabilize at 60 percent will persist and that air lines must therefore 

 leckon on making their operations satisfactory to themselves 

 financially on this basis. 



The next noteworthy item is average trip length which is ap- 

 parently stabilizing at about 400 miles, a decrease from a few years 

 ago due to a tendency recently for short-haul traffic to increase. 

 Next, there is the figure of 95 percent efficiency in completing trips 

 started. 



In figure 2 (O) there is shown the increase in air traffic against 

 Pullman traffic from a figure of just over 3 percent in 1935 to almost 

 7 percent at the present time (December 1939). As the points on 

 which this curve are based lie on a straight line, it is reasonable to 

 expect continuation of this tendency, reaching 10 percent by 1945. It 

 is possible that there will be an acceleration thereafter and several 

 have prognosticated a final flattening out at 40 or 50 percent. 

 Apropos of this possibility should be mentioned the comparison of 

 bus and rail traffic. A comparison of these two modes of travel 

 showed that but 1 percent as many people traveled by bus as by rail 

 in 1920 while by 1932 a figure of 37 percent was reached. 



Trans-Atlantic air travel has only just commenced, but in view of 

 the loads now being carried by Pan American Clippers, it can con- 

 fidently be predicted that the proportion of air to first-class boat 

 travelers will be substantial. The market is available, as recent anal- 



