B747forever
Topic Author
Posts: 13168
Joined: Mon May 21, 2007 9:50 pm

### How Far Away Can One See From A Aircraft?

I am sorry if this is not the right forum for this thread.

Let's say that a aircraft flies at FL380 on a clear day how far away can one see from the aircraft. Also if one is on the ground how far away (distance) from where the aircraft is can you see it?
Work Hard, Fly Right

Viscount724
Posts: 19315
Joined: Thu Oct 12, 2006 7:32 pm

### RE: How Far Away Can One See From A Aircraft?

Here's a calculator which should answer your questions. Just plug in the altitude to obtain the approximate distance to the horizon.
http://www.ringbell.co.uk/info/hdist.htm

B747forever
Topic Author
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Joined: Mon May 21, 2007 9:50 pm

### RE: How Far Away Can One See From A Aircraft?

 Quoting Viscount724 (Reply 1):

So when a airplane cruise at FL380 one can see about 239miles away and the airplane can be seen by people on the ground 239miles away.
Work Hard, Fly Right

Bellerophon
Posts: 522
Joined: Thu May 09, 2002 10:12 am

### RE: How Far Away Can One See From A Aircraft?

Viscount742

An interesting and useful little calculator - thanks for posting the reference - I've been playing around with it.

Cruising at max altitude, on my latest aircraft type, the horizon is 28 minutes flying time away.

Cruising at a much higher max altitude on a previous aircraft type, the horizon was only 14 minutes flying time away!

Best Regards

Bellerophon

timz
Posts: 6301
Joined: Fri Sep 17, 1999 7:43 am

### RE: How Far Away Can One See From A Aircraft?

If you're looking at Mt Shasta from FL 380 over the Central Valley it should be visible from at least 300 miles. Roughly, distance to the horizon from Mt Shasta, plus distance to the horizon from FL 380.

j0rdan
Posts: 63
Joined: Fri Feb 05, 2010 10:04 pm

### RE: How Far Away Can One See From A Aircraft?

Another formula you can use is:

Distance seen in miles = 1.23 (X) square root of altitude in feet

Jordan

timz
Posts: 6301
Joined: Fri Sep 17, 1999 7:43 am

### RE: How Far Away Can One See From A Aircraft?

That's distance to the horizon, with some allowance for refraction.

TS-IOR
Posts: 3533
Joined: Mon Oct 08, 2001 9:44 pm

### RE: How Far Away Can One See From A Aircraft?

When you are FL380 the horizon is 239NM away, but people on ground won't see you when you are 239NM from their vertical. The maximum i have ever seen from ground is contrails from approx. 80NM.

Arniepie
Posts: 1432
Joined: Thu Aug 04, 2005 11:00 pm

### RE: How Far Away Can One See From A Aircraft?

AFAIK, the answers are incomplete, for instance you can see farther on the poles vs the equator due to the shape of the earth, also air temperature changes the light behaviour properties.
I remember reading somewhere that on a cold ,clear winterday some mountains on iceland can be seen almost from 400 miles away on cruising altitude. (IIRC)

[Edited 2010-06-13 15:02:55]
[edit post]

xero9
Posts: 124
Joined: Thu Feb 22, 2007 3:12 am

### RE: How Far Away Can One See From A Aircraft?

 Quoting Arniepie (Reply 8):

Soooo in other words, you can't know for sure how far, but either way we can agree it's pretty far!

SlowFly
Posts: 1
Joined: Sun Jun 07, 2009 6:32 am

### RE: How Far Away Can One See From A Aircraft?

Some useless knowledge: a quick rule of thumb for radio line-of-right calculations is to pretend the earth's radius is 1.33 bigger than actual. Due to diffraction.

cobra27
Posts: 939
Joined: Wed May 23, 2001 6:57 pm

### RE: How Far Away Can One See From A Aircraft?

 Quoting TS-IOR (Reply 7):When you are FL380 the horizon is 239NM away, but people on ground won't see you when you are 239NM from their vertical. The maximum i have ever seen from ground is contrails from approx. 80NM.

True. No way you can see 240 miles

timz
Posts: 6301
Joined: Fri Sep 17, 1999 7:43 am

### RE: How Far Away Can One See From A Aircraft?

I've seen contrails 170+ miles away (747s making the turn over the Avenal VOR, seen from the hill above Berkeley, California). If I were standing on a higher mountain, with clear air and low sun backlighting the contrail against a fairly dark sky, 240 miles would be no problem with 10x binoculars.

http://www.jstor.org/pss/208390

[Edited 2010-06-14 14:54:36]

[Edited 2010-06-14 14:57:05]

[Edited 2010-06-14 14:59:20]

AncientPelican
Posts: 11
Joined: Sat Apr 18, 2009 12:23 am

### RE: How Far Away Can One See From A Aircraft?

I recall a TWA transcon heading westbound one evening where the pilot came on and said the people on the left side of the plane could see the lights of St Louis while those on the right could see Chicago.

unattendedbag
Posts: 2174
Joined: Wed Oct 08, 2003 10:35 pm

### RE: How Far Away Can One See From A Aircraft?

 Quoting B747forever (Thread starter):Let's say that a aircraft flies at FL380 on a clear day how far away can one see from the aircraft.

On a clear day, you can sometimes see the moon, and that's more than 238,000 miles. If it's dark outside, then you can usually see the stars.

[Edited 2010-06-22 10:31:32]
Slower traffic, keep right

rolypolyman
Posts: 85
Joined: Thu Mar 12, 2009 10:53 pm

### RE: How Far Away Can One See From A Aircraft?

I recall one night on AA in November 1996 we were at FL390 on a leg from the AEX to FZT VOR into DFW. I've been all over Texas and know the layout of cities like a map, and that's just what I was seeing with it being a particularly clear autumn night with city lights painting out the location of everything. Just before starting our descent I recognized our position as being just north of Nacogdoches. From that location I was able to easily distinguish the city lights of Waco, Temple, Austin, College Station, and Houston all at once. On the distant horizon I could distinctly see a nebulous but bright pancake smear of San Antonio, which was about 220 nm from where we were.

That was an amazing sight as I was seeing territory in one single glance that took many hours to traverse by car. It was almost like being in space. One of my best memories while flying, and definitely the furthest distance I can ever recall seeing from the air.

[Edited 2010-06-25 04:56:20]

Posts: 1566
Joined: Fri Feb 22, 2008 7:42 pm

### RE: How Far Away Can One See From A Aircraft?

Diffraction will only add about 40 miles to the distance of the horizon.
If you're flying around Tibet, all things considered, you should be able to see Everest peeking over the horizon at close to 500 miles.
Anon

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