1. Dooley's technicians centered in on a radar blip that might be Flight 11. 2. And aircrafts'primary radar blips sometimes disappear into clutter, caused by birds or other interference. 3. The radar blips were colossal waves rising up from the surface of the ocean. 4. At about 6 : 40 p . m ., radar blips of both aircraft were lost. 5. Controllers see planes passing each other at different altitudes as two radar blips converging, then diverging. 6. Suddenly, he said at a new conference, " the radar blip of both aircraft was lost ." 7. He turned to weather forecasting and became proficient at interpreting Doppler radar blips and analyzing climate patterns. 8. With that identification, the controller could then type in next to that radar blip " AA123 ." 9. With lower-flying, slower aircraft, recognizing and tracking an aircraft by its radar blips was a straightforward process. 10. Suddenly, " the radar blip of both aircraft was lost, " he said at a new conference. 
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