Original full document link 
 http://www.project1947.com/fig/airbrf.htm

PART TWO
27 Apr 1949
AIR BRIEF - SPECIAL STUDY
UNIDENTIFIED AERIAL OBJECTS
 

SECRET

Excerpt pertaining to Chiles-Whitted case:

Eastern Air Lines pilots in the air near Montgomery, Alabama, of an object resembling a V-2 in horizontal flight. While the cigar or torpedo-shaped body represents an efficient form for the fuselage of an airplane or of a guided missile, it has not been used as a primary lift-producing surface. It is estimated, however, that a fuselage of the dimensions reported by the Eastern Air Lines pilots, could support a load comparable to the weight of an aircraft of this size at speeds in the subsonic range. Although the craft sighted by these pilots was reported to be without wings and fins, it is possible that such a craft 
could be equipped with extensible wings for take-off and landing. The propulsion system of this type of vehicle would appear to be by jet or rocket, and the specific fuel consumption of such engines for this type craft would be rather high. This, coupled with the fact that aerodynamic lift on such a body would be accompanied by high drag, places a serious limitation on the range of this type of craft for any particular gross weight. If this type of unidentified aerial object has extremely long range, a method of propulsion far in advance of presently known engines would be required. 

It is believed unlikely that this and similar unexplained incidents represent a foreign craft. It seems improbable that a foreign power would expose any superior aerial weapon by a prolonged ineffectual penetration of United States, and there is no basis on which to speculate that advanced civilizations exist outside the earth and are responsible for any such activity.