During a flight this week from Kefalonia, Greece to London Gatwick, about halfway through the flight. I looked out of my window on the right of the plane and was shocked to see a Silver plane, with it appeared 1 plume out of the back, pass our plane slightly below but very close, it disappeared past the window quickly but was alarmingly close. How do I find out if this was a genuine aircraft. Its colour didn't seem very normal. Thank you.

Flight Easyjet EZY6412 on 1st September.

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    $\begingroup$ For people that are not in the aviation industry, seeing traffic pass with the required minimum vertical separation (in the US generally 1,000') can be quite startling. Pilots and flight attendants see this regularly, so it's no big deal. For most people, seeing another aircraft only 1,000 below can look like an imminent collision, but is perfectly safe. $\endgroup$
    – RetiredATC
    Sep 4, 2022 at 2:05
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    $\begingroup$ “How do I find out if this was a genuine aircraft”. I can assure you it was a genuine aircraft. $\endgroup$ Sep 4, 2022 at 2:33
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    $\begingroup$ @Minsworld You only saw one that happened to be offset on the airway to pass to the side 1000 ft above or below. Most of the traffic is perfectly centered on the airway thanks to the precision of GPS, and passes directly above or below where passengers can't see them. If you could sit in the flight deck like in the old days, you'd freak out because they look like they're coming straight at you until they get a mile or so away and it becomes obvious they are above or below you. $\endgroup$
    – John K
    Sep 4, 2022 at 4:24
  • $\begingroup$ How “close” do you estimate that was? What type of aircraft was it? An airliner or something a lot smaller? $\endgroup$
    – jcaron
    Sep 4, 2022 at 13:55

2 Answers 2


I know that Flightradar24 has a history function in its paid subscriptions that enables you to view paths of past flights. I do not have this so unfortunately I will not be able to help here.

As stated in many comments, "close" encounters such as this are common, and as air traffic returns to its pre pandemic level, they will be very common. They pose no threat to safety as long as any of the multiple safety features built into aviation industry is active.

One contrail may suggest a single engine jet, or one that has engines relatively close to each other. There is a remote possibility that this jet was a military aircraft, which may not show on any flight trackers as they have the possibility to hide their presence from tracking systems. If it was a fighter jet, there was even less of a chance for a collision, due to the systems delivering highly accurate data of the surroundings to the pilot.

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    $\begingroup$ As someone who does have a paid subscription, there were two or three such encounters during the first hour of the flight alone. $\endgroup$
    – Sanchises
    Sep 4, 2022 at 16:32

The exact rules vary based on altitude, area, type of flight, etc, but the rule lost likely applicable in your case is that flights are on flight levels (FL) which are multiples of ten, either an odd multiple of ten (FL270, FL290, FL310…) if they have a heading between 0 and 179 degrees, or an even multiple of ten (FL260, FL280, FL300…) otherwise.

Flight levels are multiples of 100 feet.

So you could have one flight heading west or north-west like yours on FL260 (26000 feet) while another flight is heading east on FL250 (25000 feet). That’s a difference of 1000 feet, roughly 300m.

If both planes were heading in (roughly) the same direction, it would be double.

Given the size of aircraft, one flying 300m from yours may seem extremely close, but there’s no risk there, this is just regular operations.

Another possibility if the aircraft was A LOT closer (but probably a lot smaller) is that there was some kind of situation (e.g. radio malfunction) and a military jet was sent to check if everything was alright. But that’s quite the rare occurrence, and since you apparently got to your destination without trouble, nothing bad happened.


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