Why are fighter jets flying today?

A fighter pilot needs a minimum number of sorties every month to remain combat-ready, and a wing with two or three squadrons flies hundreds of sorties a month. Most of what you see over an air base, a training range or a low-level route is therefore ordinary work: air-combat manoeuvring against another pair, practice approaches, night flying, formation flying or air-to-air refuelling. Flying is concentrated on weekdays and in daylight, with night periods scheduled a few weeks a year, and bases usually post a weekly flying schedule or noise advisory on their website.

Some days are visibly heavier. Large exercises, such as Red Flag at Nellis, Frisian Flag in the Netherlands or NATO's Air Defender, bring dozens of jets from several countries into one area for two or three weeks and generate constant traffic. Visiting squadrons on deployment, aircraft repositioning ahead of a hurricane, or a wing surging before an overseas rotation also raise the tempo. National holidays, remembrance days and major sporting finals add ceremonial flyovers, which are announced in advance and flown in close formation.

A small share of flights are alert launches: fighters scrambled to check an aircraft that lost radio contact or wandered into restricted airspace, or to escort a foreign military aircraft near national borders, as happens regularly over the Baltic or off Alaska. Those flights are unplanned and often low and fast. To identify a flight, check the NOTAMs for your area, which list restricted zones and exercises; flight-tracking sites, which show tankers and support aircraft; and the public-affairs feeds of the nearest base, which explain unusual activity within hours.