flew / flu are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
flew: (verb) travel through the air; be airborne. (verb) move quickly or suddenly. (verb) operate an airplane. (verb) transport by aeroplane. (verb) cause to fly or float. (verb) be dispersed or disseminated. (verb) change quickly from one emotional state to another. (verb) pass away rapidly. (verb) travel in an airplane. (verb) display in the air or cause to float. (verb) travel over (an area of land or sea) in an aircraft. (verb) hit a fly.
flu: NA
flew: f·l·UW
flu: f·l·UW
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)