Beacons, Lighting and Glideslope Aids

A rotating beacon marks an airport when it is dark or visibility is low. Alternating white and green flashes mean a lighted civilian land airport; white and yellow means a water airport; and two whites plus a green means military. A subtle but important rule: a rotating beacon operating during daylight hours normally indicates that the weather in the Class B, C, D, or E surface area is below basic VFR minimums — a ceiling less than 1,000 feet and/or visibility less than 3 miles — but this is not a substitute for obtaining an actual weather report or checking the weather yourself. Lighting is color-coded too: runway edge lights are white, taxiway edge lights are blue, taxiway centerline lights are green, and runway end lights read green on approach and red from the far end. Finally, visual glideslope aids keep you on a safe descent. A VASI shows "red over white, you are all right," red over red when too low, and white over white when too high. A PAPI is a single horizontal row of four lights that shows four red when low, four white when high, and two white / two red when on the glidepath.