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 How Far Away Can One See From A Aircraft?
 B747forever From Sweden, joined May 2007, 17695 posts, RR: 10Posted Sat Jun 12 2010 12:57:31 UTC (5 years 11 months 2 weeks 3 days 14 hours ago) and read 23212 times:

 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 From Switzerland, joined Oct 2006, 29459 posts, RR: 24 Reply 1, posted Sat Jun 12 2010 14:36:48 UTC (5 years 11 months 2 weeks 3 days 13 hours ago) and read 23169 times:

 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 From Sweden, joined May 2007, 17695 posts, RR: 10 Reply 2, posted Sat Jun 12 2010 14:50:33 UTC (5 years 11 months 2 weeks 3 days 12 hours ago) and read 23154 times:

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 From United Kingdom, joined May 2002, 587 posts, RR: 58 Reply 3, posted Sat Jun 12 2010 15:32:46 UTC (5 years 11 months 2 weeks 3 days 12 hours ago) and read 23134 times:

 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 From United States of America, joined Sep 1999, 7222 posts, RR: 7 Reply 4, posted Sat Jun 12 2010 17:03:33 UTC (5 years 11 months 2 weeks 3 days 10 hours ago) and read 23073 times:

 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 From Canada, joined Feb 2010, 127 posts, RR: 0 Reply 5, posted Sat Jun 12 2010 17:27:10 UTC (5 years 11 months 2 weeks 3 days 10 hours ago) and read 23057 times:

 Another formula you can use is: Distance seen in miles = 1.23 (X) square root of altitude in feet Jordan
 timz From United States of America, joined Sep 1999, 7222 posts, RR: 7 Reply 6, posted Sun Jun 13 2010 14:06:55 UTC (5 years 11 months 2 weeks 2 days 13 hours ago) and read 22725 times:

 That's distance to the horizon, with some allowance for refraction.
 TS-IOR From Tunisia, joined Oct 2001, 3731 posts, RR: 5 Reply 7, posted Sun Jun 13 2010 14:23:57 UTC (5 years 11 months 2 weeks 2 days 13 hours ago) and read 22714 times:

 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 From Belgium, joined Aug 2005, 1292 posts, RR: 1 Reply 8, posted Sun Jun 13 2010 15:01:47 UTC (5 years 11 months 2 weeks 2 days 12 hours ago) and read 22695 times:

 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 From Canada, joined Feb 2007, 161 posts, RR: 0 Reply 9, posted Sun Jun 13 2010 17:47:02 UTC (5 years 11 months 2 weeks 2 days 10 hours ago) and read 22613 times:

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

 SlowFly From South Africa, joined Jun 2009, 15 posts, RR: 0 Reply 10, posted Mon Jun 14 2010 12:55:01 UTC (5 years 11 months 2 weeks 1 day 14 hours ago) and read 22360 times:

 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 From Slovenia, joined May 2001, 1103 posts, RR: 0 Reply 11, posted Mon Jun 14 2010 13:55:37 UTC (5 years 11 months 2 weeks 1 day 13 hours ago) and read 22314 times:

 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 From United States of America, joined Sep 1999, 7222 posts, RR: 7 Reply 12, posted Mon Jun 14 2010 14:53:08 UTC (5 years 11 months 2 weeks 1 day 12 hours ago) and read 22279 times:

 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 From United States of America, joined Apr 2009, 34 posts, RR: 0 Reply 13, posted Tue Jun 22 2010 10:20:09 UTC (5 years 11 months 1 week 17 hours ago) and read 21723 times:

 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 From United States of America, joined Oct 2003, 2400 posts, RR: 1 Reply 14, posted Tue Jun 22 2010 10:29:07 UTC (5 years 11 months 1 week 17 hours ago) and read 21721 times:

 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 From United States of America, joined Mar 2009, 160 posts, RR: 0 Reply 15, posted Fri Jun 25 2010 04:54:47 UTC (5 years 11 months 4 days 22 hours ago) and read 21457 times:

 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]
 nomadd22 From United States of America, joined Feb 2008, 2142 posts, RR: 0 Reply 16, posted Fri Jun 25 2010 10:21:23 UTC (5 years 11 months 4 days 17 hours ago) and read 21396 times:

 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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