Context: The first lighting used on an airport was during the latter part of the 1920s; in the 1930s approach lighting came into use. These indicated the proper direction and angle of descent. The colours and flash intervals of these lights became standardized under the International Civil Aviation Organization (ICAO). In the 1940s, the slope-line approach system was introduced. This consisted of two rows of lights that formed a funnel indicating an aircraft's position on the glideslope. Additional lights indicated incorrect altitude and direction.

Question: When was the first lighting used on an airport?
Answer: latter part of the 1920s

Question: When did approach lighting come into use?
Answer: 1930s

Question: What indicated the proper direction and angle of descent?
Answer: approach lighting

Question: When was the slope-line approach system introduced?
Answer: 1940s

Question: What consisted of two rows of lights that formed a funnel, indicating an aircraft's position on the glidescope?
Answer: slope-line approach system

Question: When was the first  lighting with flash intervals used on an airplane?
Answer: Unanswerable

Question: What was standardized by airports in the 1920's?
Answer: Unanswerable

Question: What did the flash interval system consist of?
Answer: Unanswerable

Question: What do light colors indicate on an aircraft?
Answer: Unanswerable

Question: What group standardized additional indication lights?
Answer: Unanswerable