Langley Ave and Halsey Ave

Mystery question of the day (as a follow up to the previous post). Most of the streets in the presidential section are aptly named after presidents (i.e. Adams, Madison, Jackson, Harding, Grant(land), McKinley, Roosevelt, Coolidge, Wilson, Tyler Pl.). The two noted exceptions are Langley Ave. and Halsey Ave. Older street maps of WH show that these two streets were originally called Lincoln Ave and Harrison Ave, respectively. When zip codes were later introduced and the postal system became formalized, the people in charge assumedly didn't want there to be confusion with other streets of the same name within one zip code. Since a street named Lincoln already existed in the Hempstead Gardens section, and another named Harrison south of Eagle Ave, they chose different names for those two streets. But who are Langley and Halsey after whom the two streets are now named?