# Did we get closer to another plane than we were supposed to, or was the pilot just protecting our delicate sensibilities?

Yesterday, April 28, 2019, I was flying on Alaska flight 557 from LAX to PDX.

About an hour into the flight (near the California/Oregon border) I was looking out the window and saw a jet travelling the opposite direction from us. It was travelling exactly the opposite direction of us and I saw it when it was ~45-60 degrees forward of us.

Within a couple of seconds of my seeing it, we banked sharply to the right. It was not a violent turn; An answer to this question describes true evasive maneuvers as, "those of you not strapped down would have been hurled to the ceiling or slammed to the floor and your stomach would be heaving in a different direction from the rest of you." - and we didn't have anything like that. I'm not sure I would have even noticed the turn had I not been looking out the window.

However, it was a pretty sharp mid-flight maneuver, and because I was over the wing, I didn't get to see the other airplane at closest approach because the wing blocked my view. I would estimate that it was about 3-5000 feet away from us. I felt like he was at pretty close to our altitude, but again, as the linked question says, that's hard to say for sure.

The linked question points out that distances and altitude differences are hard to judge. That's fair, so I'll offer the following bona fides:

• I live about half a mile from a commercial airport, perpendicular to the end of the runway, so I have a good idea of what jets that are half a mile away from me look like. I would estimate that the other jet was a bit but not a lot further away than that.
• If two jets pass by each other at 1/2 mile, and you can see another jet that is 60 degrees in front of or behind you, and he, like us, was travelling 480 mph, he would have been in my field of vision for 6.5 seconds. That sounds about like what I remember. At 3 miles, that number turns into 40 seconds. I don't remember the exact amount of time, but my initial estimate before I did this math was 8 seconds.

I could imagine our pilot banking the plane simply to lessen the odds of the passengers noticing a safe encounter, as even a safe encounter leads to awkward questions on sites like this.

So, my question: Did we have a near miss, or was this a standard close-but-intended encounter?

• The answer to this very similar question is a good one: aviation.stackexchange.com/questions/3680/… Apr 29 '19 at 23:23
• Thanks for posting the # and specifics, often these questions omit those crucial details. Did you happen to see any details of the other plane? Airline logo, etc.? Was there any weather in the vicinity, such as thunderstorms? Apr 29 '19 at 23:48
• Clear blue skies, minimal turbulence. I couldn't see what airline the other plane was. Apr 30 '19 at 0:26
• What makes you think the turn had anything to do with the other aircraft at all? You were probably just turning to follow your route. Planes turn multiple times during a flight. And sorry, but the fact that you live close to an airport does not mean you are qualified to determine the vertical distance between two aircraft in the air, which would be especially difficult during a turn since your frame of reference would be tilted. Apr 30 '19 at 9:19
• The basic rule of aircraft (and ship) collision avoidance is "if the thing you are looking at is moving across your field of vision, you aren't going to hit it". So if you see something 45 degrees way from your plane's course and travelling parallel to your plane in the opposite direction (and therefore the 45 degree angle will be increasing), that is nothing to worry about. Apr 30 '19 at 10:28

From the flightradar24 playback, it appears to have been an encounter with Etihad Airways 171.

Your flight (Alaska) was at FL360, while the opposing was at FL370. Therefore, there was 1000 feet of vertical separation between them, which is typically considered safe when operating with RVSM, Reduced Vertical Separation Minima rules (see other answers).

I also looked up the LiveATC recordings archive (Seattle Centre Sector 14 high, 28/04 2000Z), and found a clip that I think corresponds to the event:

• Alaska 557, can we take a heading right of course to avoid some wind?
• Affirmative
• Ok, deviation approved [...]
• The other answer is good because it applies generally, but I like this one a lot; it directly reassures OP that everything was safe.
– Tim
Apr 30 '19 at 10:09
• Also, to a casual observer, other aircraft often appear to be much closer than they actually are. People are used to cars and fail to appreciate how the lack of visual references and the size contrast play with their perceptions.
– J...
Apr 30 '19 at 12:12
• FLNaN undefined passing near Hackamore makes one wonder... :) Apr 30 '19 at 15:16
• I actually wonder now if the "wind" on the radio is wake turbulence from the 777. Is 1000 feet a reasonable separation to avoid that? It wouldn't have to be dangerous necessarily, just a pilot wanting to keep his passengers comfortable. Apr 30 '19 at 15:59
• @AricTenEyck two nanometers is awfully close for a pair of tin cans moving at 1000 km/h relative to each other... Apr 30 '19 at 17:15

It's unlikely. Because of RVSM, Reduced Vertical Separation Minima rules, the vertical distance between airplanes passing each other is only 1000 ft. If you were in the flight deck so you could see out front, you'd be having a wonderful time freaking out because airplanes on the same airway pass above and below going the other direction only 1000 ft away. And when they pass over 1000 ft away it looks like 300 the first few times you experience it.

Plus, thanks to GPS, everybody is exactly on the center of the airway all the time, so every oncoming airplane seems to be coming straight at you until they are a couple miles away and when they go by they are perfectly lined up above or below (the passengers rarely see them all as a result and have no idea that they are regularly are passing other aircraft close by like cars on a highway).

Same with airplanes crossing your track, or going the opposite way on an offset track (those are the ones that passengers see). If they happen to pass directly above or below, or close by going the other way, same deal - only 1000 ft above or below if they are on the next flight level and it looks like they are right next to you.

The other thing is that collision avoidance systems (TCAS) give a climb or descend instruction when there is a need to take evasive action, not a turn, so if there was an actual TCAS event you'd be pressed into your seat or coming out of it, not turning.

That being said, it is possible that one of the crew saw something visually and decided to maneuver laterally to avoid it (it was likely someone hand flying because autopilot turns are pretty gentle), but keeping in mind that fact that airplanes normally pass really close vertically, and serious evasive action usually results in stuff flying about inside, it's a good chance that what you saw was normal.

• Who knows? They could have been avoiding someone, or ATC could have asked for a fast heading change to avoid a conflict. My point was just not to make assumptions because you see other airplanes nearby. If there was something serious there is likely an incident report. I know of a Dash 8 that encountered some sort of unmanned drone at 15 or 20000 ft and pushed over to avoid it, injuring the FA. Apr 30 '19 at 1:15
• @AricTenEyck Planes do tend to turn every once in a while. It makes it easier to hit the right airport. It has nothing to do with other planes that are vertically separated. Apr 30 '19 at 9:13
• FYI, auto of autopilot in RVSM space is mandatory--no hand flying. Apr 30 '19 at 18:08
• If you're in RVSM and you get a TCAS RA, or you see something you need to avoid right now, you are disconnecting and hand flying post haste, RVSM or not. May 1 '19 at 0:57
• @AricTenEyck Queue Monty Python skit: "Captain, I see on the manifest that avid Aviation StackExchange user AricTenEyck is in seat 10". "Roger that, executing hard right turn, that'll give him something to talk about!" "Just as that 777 is coming up on our left! Teeheeheeheehee!" "NEAR MISS!!" Teeheeheehee" "Oh, you forgot to turn on the cabin mic..." "Oh... well maybe next time!" May 1 '19 at 19:47

The Etihad flight was a 777, which is a much larger aircraft, but of almost the same proportions as the 737. Also living near an airport, I am well familiar with how difficult it is to gauge altitude. You see airplanes apparently moving at quite different speeds; actually a "slow" plane is moving at a similar speed but is larger and farther away. It's really a problem in open air, with no reliable visual references for size.

So I suspect you saw the same optical illusion, where the 777 seemed closer simply because of its large size. That said, it was quite close vertically - 1000 feet separation. The horizontal separation did not matter because the vertical separation was sufficient.

It's quite possible the wake turbulence from that huge 777 was of concern to the Alaska pilot, so he deviated (with permission) to avoid it.