Therefore, it should come as no surprise that Longbottom was keenly interested in condensation trails.
Thus, on Christmas day 1939, over two years before the publication of Flight to Arras, Longbottom issued a SECRET report titled "Condensation Trails at High Altitudes" which begins by explaining the major implication of contrails for air warfare: a contrail aids enemy defenders by betraying the position of an aircraft that might otherwise be invisible.
A measure of the continuing importance of condensation trails is the series of contrail studies sponsored by the ARC.
For whatever reason, in September 1942, NACA's Langley Memorial Aeronautical Laboratory issued a report on condensation trails.
Additionally, a section of the report discussed the possibility of suppressing condensation trails. Where the exhaust trails were concerned, the report stated that the only reliable means of preventing their formation was to remove the water from engine exhausts by means of a water-recovery system.
At times, planes near the end of the bomber stream had to complete their bomb runs by flying through condensation trails "so dense that it was no different than flying in clouds." Furthermore, these vapor trails could be so persistent that bomber formations sometimes took different routes on their return legs to avoid "the contrail clouds that we created." Apropos of this point, a pilot in the 457th Bomb Group later wrote: "We often said that we created weather over Europe." (54)
Even then, Williamson wrote, "appalling weather, [along] with condensation trails that made formation flying virtually impossible, forced the recall of the bulk of the force." (59)
As already noted in Part I of this paper, condensation trails had been encountered at ground level in Canada as early as 1930.
Dense condensation trails could be seen up in the stratosphere.
Pearson, Condensation Trails: Where They Occur and What Can Be Done about Them," National Advisory Committee for Aeronautics Wartime Report, Sep 1942, p.
Longbottom, "Condensation Trails at High Altitudes," Dec 25, 1939, United Kingdom Archives, Document AIR 20/321, p.
Dobson, Meteorology Subcommittee of the Aeronautical Research Committee, "Condensation Trails from Aeroplane Engine Exhaust and Meteorological Conditions," Feb 7, 1941, United Kingdom Archives, Document DSIR 23/10802, p.