50 USc § 3024(1) (U) UAP Collection Challenges (U) Sociocultural stigmas and sensor limitations remain obstacles to collecting data on UAP. Although some teclmical challenges-such as how to appropriately filter out radar clutter to ensure safety of flight for military and civilian aircraft-are longstanding in the aviation community , while others are lullque to the UAP problem set. • (U) Narratives from aviators in the operational community and analysts from the military and Ie describe disparagement associated with obselving UAP rep0l1ing it or attempting to discuss it with colleagues. Although the effects of these stigmas have lessened as senior members of the scientific policy military and intelligence comlmmities engage on the topic seriously in public , reputational risk may keep nn., .. r" ... r., silent, complicating scientific pursuit of the topic. The sensors mOlmted on U.S. military platforms are typically designed to fulfill specific missions often • (U) Sensor vantage points and the numbers of sensors conclUTently obselving an object play substantial roles in distinguishing UAP from known objects and determining whether a UAP demonstrates breakthrough aerospace capabilities. Optical sensors have the benefit of providing some insight into relative size , shape and structure. Radiofrequency sensors provide more accurate velocity and range information. (U) But Some Potential Patterns Do Emerge (U) Although there was wide variability in the repol1s and the dataset is clUTently too limited to allow for detailed trend or pattern analysis there was some clustering ofUAP obselvations regarding shape , size , and , particularly , propulsion . UAP sightings also tended to cluster around U.S. training and testing grounds , but we assess that this may result ii-om a collection bias as a result of focused attention , greater numbers of latest-generation sensors operating in those areas lullt expectations , and guidance to report anomalies. most common shape described by military personnel in their rep0l1ing was all. (See Figure 1.) . Militatyaviators described many ofthesell'M objects as 1 ~(a) that Several sightings were lilfil. shapes like all'l5I or a 5 50 USC § 302~( 1 )