Aviation runs on the 24 hour clock. Every flight plan, weather report, air traffic control instruction, and airport schedule in the world uses military time. If you’re a pilot, flight student, aviation enthusiast, or frequent flyer trying to read a departure board in Europe, this guide explains how the 24 hour clock works in the aviation industry.
Why Aviation Uses Military Time
A commercial flight from New York to Tokyo crosses multiple time zones and might depart in the evening and arrive the next morning. If the pilot and air traffic control were using AM and PM, the opportunities for confusion would be endless.
Aviation solved this decades ago by adopting two standards: the 24 hour clock for all time references, and Zulu Time (UTC) as the universal time zone.
When a pilot files a flight plan, the departure and arrival times are in 24 hour format referenced to Zulu Time. A flight departing at 2230Z means 10:30 PM UTC, regardless of what the local time is at the departure airport. The arrival airport, the air traffic controllers en route, and the airline’s operations center all read that same number the same way.
No AM. No PM. No timezone confusion. Just a four digit number and a Z.
How the 24 Hour Clock Shows Up in Aviation
Flight Plans
Every flight plan filed anywhere in the world uses military time in Zulu. A typical flight plan includes:
Estimated departure time: 1430Z Estimated en route time: 0345 (3 hours 45 minutes) Estimated arrival time: 1815Z
These times are in UTC so that every facility handling the flight, from departure to arrival, is working from the same clock.
Air Traffic Control Communications
Pilots and controllers communicate times in 24 hour format constantly. A few examples of what you might hear:
“Cleared for takeoff runway two seven, time check one four three two Zulu.”
“Expect arrival at the fix at zero eight forty five.”
“Contact approach on one two four point five at two one hundred.”
Times are spoken digit by digit or as hundreds. 1432 is “fourteen thirty two.” 0845 is “zero eight forty five.” 2100 is “twenty one hundred.”
Interactive Tool: Zulu Time Flight Planner
METARs and Weather Reports
Aviation weather reports (called METARs) are issued in Zulu Time. A METAR for an airport might read:
KJFK 271856Z 31012KT 10SM FEW250 22/11 A3012
The “271856Z” means this report was issued on the 27th day of the month at 1856 Zulu (6:56 PM UTC). A pilot in any timezone can read this and know exactly when the observation was taken.
TAFs (Terminal Aerodrome Forecasts) work the same way. They cover future weather in blocks of Zulu Time:
FM272200 meaning “from the 27th at 2200Z” TL280400 meaning “until the 28th at 0400Z”
NOTAMs
Notices to Air Missions (NOTAMs) alert pilots to hazards, closures, and changes at airports. Every NOTAM includes effective times in Zulu.
A runway closure NOTAM might read: “RWY 09/27 CLSD 0600-1400Z DAILY.” That means the runway is closed from 6:00 AM to 2:00 PM UTC every day. A pilot needs to convert that to local time to know if it affects their departure or arrival.
Airport Departure Boards
If you’ve ever flown internationally, you’ve seen 24 hour time on departure boards. A flight listed as departing at 17:45 means 5:45 PM local time. In most of the world, this is completely normal. In the US, some airports show both formats, but the airline’s internal systems always use 24 hour time.
Zulu Time: Aviation’s Universal Clock
Zulu Time is UTC (Coordinated Universal Time). It’s called Zulu because Z is the military time zone letter for UTC, and Zulu is the NATO phonetic alphabet word for Z.
Every major aviation time reference uses Zulu. Flight plans, weather reports, NOTAMs, air traffic control clearances, and flight logs all default to Zulu Time unless specifically stated otherwise.
This matters because aviation is global. A flight from London to Dubai crosses three time zones. The departure airport, the arrival airport, and every air traffic control center in between could all be in different local times. Zulu Time gives everyone a single reference point.
When a controller says “expect the runway at 1500 Zulu,” both the pilot and the controller know exactly what that means, even if the controller is in London (where local time is 1500 in winter) and the pilot’s destination is Dubai (where local time is 1900).
Common Aviation Times
0000Z to 0600Z — Overnight hours in UTC. Airports in Europe and Africa are in the early morning. US airports are still in the evening of the previous day.
0600Z — Many European airports begin their morning rush. Weather reports start cycling more frequently.
1200Z — Noon UTC. The midpoint of the Zulu day. US East Coast is at 0700 or 0800 local (depending on DST), meaning the morning departure push is starting in America.
1800Z — Early afternoon in UTC. US airports are in peak operations. European airports are winding down evening operations.
Standard Zulu conversions for US pilots: Eastern: Zulu minus 5 (winter) or minus 4 (summer) Central: Zulu minus 6 (winter) or minus 5 (summer) Mountain: Zulu minus 7 (winter) or minus 6 (summer) Pacific: Zulu minus 8 (winter) or minus 7 (summer)
How Pilots Learn Military Time
Military time is introduced early in flight training. Student pilots learn to read METARs, file flight plans, and communicate with ATC using 24 hour format from their first ground school lessons.
Most flight training programs teach Zulu Time conversion as a core skill. Student pilots practice converting between local time and Zulu until it becomes automatic. By the time a pilot gets their private license, reading 1347Z as “1:47 PM UTC” is as natural as reading a regular clock.
A few tips that flight instructors commonly share:
Write Zulu conversions on your kneeboard. Before every flight, write down the current Zulu offset for your airport. If you’re on the East Coast in winter, write “Local plus 5 equals Zulu” and keep it visible.
Check METAR times against your watch. When you pull a weather report, glance at the Zulu timestamp and convert it. If it doesn’t match roughly with your current time plus offset, something is wrong and you might be reading an outdated report.
Use Zulu for all your planning. Even for local flights, practice thinking in Zulu. It builds the habit so that when you start flying cross country or instrument approaches, the conversion is already second nature.
The Connection Between Military Time and Aviation
The military and aviation have been linked since the beginning of flight. Military pilots were among the first to adopt the 24 hour clock, and when commercial aviation expanded after World War II, it brought military timekeeping standards with it.
Today, military aviation and civilian aviation use the exact same time conventions. A Navy pilot landing on an aircraft carrier and a commercial pilot landing at JFK are both communicating in 24 hour Zulu Time. The systems are identical because they were built on the same foundation.
The NATO phonetic alphabet also crossed over from military to aviation. When a pilot reads back a flight number or a taxiway letter, they use Alpha, Bravo, Charlie, just like a soldier on a radio. The 24 hour clock and the phonetic alphabet are two halves of the same communication system designed to prevent deadly mistakes.
Need a quick reference? Check out the complete military time chart with all 24 hours, or use our instant converter to look up any time in seconds.
