Phoenix is the capital and largest city of Arizona and the seat of Maricopa County. It sits in the Salt River Valley, the desert basin nicknamed the "Valley of the Sun," and had 1,608,139 residents at the 2020 census, making it the fifth-most populous U.S. city and the most populous state capital. Its metropolitan area holds close to five million people. Phoenix Sky Harbor International Airport, owned by the city since 1935, is the region's main airport, and Luke Air Force Base, which trains fighter pilots, lies on the valley's west side.

The Hohokam people farmed the valley for about two thousand years and dug roughly 135 miles of irrigation canals. The modern city was settled in 1867, incorporated in 1881, named territorial capital in 1889, and became the state capital at statehood in 1912. World War II brought training airfields such as Luke Field, and the dry, clear desert has remained a center of military flight training. Ranges to the southwest include the Barry M. Goldwater Range, where military aircraft drop illumination flares during night training.

That mix of open skies, military training, and a large population shaped the Phoenix Lights of March 13, 1997. Between about 7:30 and 10:30 p.m., people across roughly 300 miles of Arizona reported lights, first a V-shaped formation passing over the state around 8 p.m., then a row of stationary lights over Phoenix around 10 p.m. Military accounts attribute the formation to A-10 jets in an Air National Guard training program and the later lights to flares dropped over the Goldwater range, an explanation many witnesses reject for the earlier phase. Governor Fife Symington mocked the reports at a 1997 news conference, then said in 2007 that he had seen an unexplained craft himself. Actor Kurt Russell, a pilot, has said he reported the lights to air traffic control while flying into Sky Harbor. Later light displays over the valley in 2007 and 2008 were attributed to F-16 flares from Luke and to flares tied to balloons.

The 1997 case still drew fresh attention in 2026, as clips of Russell's account recirculated and residents posted new accounts and videos of triangles and blinking lights over the city, none of them independently identified. Phoenix's significance is that a major metropolitan area beside busy military training airspace produced one of the best-known mass UFO sightings in American history, and it remains the reference point against which new sightings over the valley are measured.