Editing Instrument landing system (section)

===Limitations===
Due to the complexity of ILS localizer and glide slope systems, there are some limitations. Localizer systems are sensitive to obstructions in the signal broadcast area, such as large buildings or hangars. Glide slope systems are also limited by the terrain in front of the glide slope antennas. If terrain is sloping or uneven, reflections can create an uneven glidepath, causing unwanted needle deflections. Additionally, since the ILS signals are pointed in one direction by the positioning of the arrays, glide slope supports only straight-line approaches with a constant angle of descent. Installation of an ILS can be costly because of siting criteria and the complexity of the antenna system.

[[Critical area (airport)|ILS critical areas]] and ILS sensitive areas are established to avoid hazardous reflections that would affect the radiated signal. The location of these critical areas can prevent aircraft from using certain taxiways<ref>[https://web.archive.org/web/20150109002149/https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/systemops/atpac/media/ATPAC_Areas_of_Concern-116-3.pdf FAA, ''ILS Glide Slope Critical Area Advisory'' (archived)]: pg 4, ILS Course Distortion</ref> leading to delays in takeoffs, increased hold times, and increased [[Separation (air traffic control)|separation between aircraft]].