# Airplane Smoke Trail? **URL:** \ **Category:** Factual Questions\ **Created:** [February 24, 2006, 7:36pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957 "2006-02-24T19:36:31Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![jali](https://avatars.discourse-cdn.com/v4/letter/j/ecae2f/32.png) [@jali](https://boards.straightdope.com/u/jali)\ **Post date:** [February 24, 2006, 7:36pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/1 "2006-02-24T19:36:31Z")
When I’m looking up at different airplanes (I live close to an airport) only some of the planes leave that telltale white smoke emission trail. Sometimes it seems as though 4 or 5 planes are flying close to the same altitude (in different directions) and usually I can see the trail from only 1 of the airplanes. Why? Could my eyes be playing tricks? Perhaps the altitude differs by more than I’m thinking. Please clear this up for me - I don’t smoke inside my home, so I’m outside looking at airplanes on a regular basis and it’s starting to bug me. Thank you, oh wise and wonderous Oz. ---
**Author:** ![Dorjan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dorjan/32/12440_2.png) [@Dorjan](https://boards.straightdope.com/u/Dorjan)\ **Post date:** [February 24, 2006, 7:44pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/2 "2006-02-24T19:44:12Z")
Those are condensation trails from the engine, not smoke trails. They only show up when the outside air is at a certain humidity and density, which varies w/ altidude. I don’t remember exactly but you usually get them at around 33,000 - 40,000 feet. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [February 24, 2006, 7:45pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/3 "2006-02-24T19:45:39Z")
Google “contrails”. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [February 24, 2006, 7:46pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/4 "2006-02-24T19:46:51Z")
They are called contrails and here is a description: [http://cimss.ssec.wisc.edu/wxwise/class/contrail.html](http://cimss.ssec.wisc.edu/wxwise/class/contrail.html) ---
**Author:** ![The\_Chao\_Goes\_Mu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_chao_goes_mu/32/3191_2.png) [@The\_Chao\_Goes\_Mu](https://boards.straightdope.com/u/The_Chao_Goes_Mu)\ **Post date:** [February 24, 2006, 7:49pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/5 "2006-02-24T19:49:50Z")
Not to be confused with [tinfoil hat on]Chemtrails[/tinfoil hat off] ---
**Author:** ![jali](https://avatars.discourse-cdn.com/v4/letter/j/ecae2f/32.png) [@jali](https://boards.straightdope.com/u/jali)\ **Post date:** [February 24, 2006, 7:51pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/6 "2006-02-24T19:51:16Z")
Thank you guys! Very interesting article. You are truly fighting ignorance. (I’d never heard of a contrail) ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [February 24, 2006, 8:02pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/7 "2006-02-24T20:02:25Z")
> [@jali](#): > > Thank you guys! Very interesting article. You are truly fighting ignorance. (I’d never heard of a contrail) I am sure contrail heard of you though. That is the scary part. ---
**Author:** ![jali](https://avatars.discourse-cdn.com/v4/letter/j/ecae2f/32.png) [@jali](https://boards.straightdope.com/u/jali)\ **Post date:** [February 24, 2006, 8:07pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/8 "2006-02-24T20:07:32Z")
> [@Shagnasty](#): > > I am sure contrail heard of you though. That is the scary part. I finally “get” your name. Cracks me up! ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [February 24, 2006, 8:42pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/9 "2006-02-24T20:42:54Z")
And if you see white ‘smoke’ coming from the wingtips when an airplane is landing, it’s condensation trails caused by the wingtip vortices. ---
**Author:** ![Mindfield](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mindfield/32/19759_2.png) [@Mindfield](https://boards.straightdope.com/u/Mindfield)\ **Post date:** [February 24, 2006, 8:52pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/10 "2006-02-24T20:52:43Z")
And if you see white ‘smoke’ coming from the cockpit, run like hell. ---
**Author:** ![Dorjan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dorjan/32/12440_2.png) [@Dorjan](https://boards.straightdope.com/u/Dorjan)\ **Post date:** [February 24, 2006, 10:47pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/11 "2006-02-24T22:47:32Z")
Unless it’s an Air Jamaica plane… ---
**Author:** ![KlondikeGeoff](https://avatars.discourse-cdn.com/v4/letter/k/3e96dc/32.png) [@KlondikeGeoff](https://boards.straightdope.com/u/KlondikeGeoff)\ **Post date:** [February 24, 2006, 10:57pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/12 "2006-02-24T22:57:42Z")
> [@The Chao Goes Mu](#): > > Not to be confused with [tinfoil hat on]Chemtrails[/tinfoil hat off] Yeah, this is a hilarious conspiracy theory by the nutcases. One part of the theory claims that when you see two trails crossing, at the cener of the X is where the guv’ment bad guys make the chemicals come down and poison you, so be sure not to hang around under that X. 😃 ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [February 25, 2006, 12:17am UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/13 "2006-02-25T00:17:59Z")
> [@Dorjän](#): > > Those are condensation trails from the engine, not smoke trails. They only show up when the outside air is at a certain humidity and density, which varies w/ altidude. I don’t remember exactly but you usually get them at around 33,000 - 40,000 feet. They happen pretty frequently below that; WWII bombers would often leave contrails, and they didn’t fly that high. ---
**Author:** ![A.R.Cane](https://avatars.discourse-cdn.com/v4/letter/a/ee7513/32.png) [@A.R.Cane](https://boards.straightdope.com/u/A.R.Cane)\ **Post date:** [February 25, 2006, 12:52am UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/14 "2006-02-25T00:52:14Z")
When I was a kid, in the 40’s, it was common for people, especially kids, to look up at planes as they were much rarer than today, especially jets. My father would sometimes say things designed to spark my imagination and I recall him telling me that if I could find a way to eliminate contrails I would be rich. The curiosity stuck w/ me, but I never did get rich. I have an additional question though. Are stealth aircraft designed to minimize contrails? ---
**Author:** ![Scruloose](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@Scruloose](https://boards.straightdope.com/u/Scruloose)\ **Post date:** [February 25, 2006, 1:27am UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/15 "2006-02-25T01:27:50Z")
> [@A.R. Cane](#): > > I have an additional question though. Are stealth aircraft designed to minimize contrails? Apparently, [they are.](http://boards.straightdope.com/sdmb/showthread.php?t=347075) (see **thinksnow’s** link) ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [February 25, 2006, 1:31am UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/16 "2006-02-25T01:31:13Z")
> [@A.R. Cane](#): > > When I was a kid, in the 40’s, it was common for people, especially kids, to look up at planes … Heh. I was at a family reunion once where every time an airplane flew over I looked up. My mom looked up. Dad looked up. Mom’s husband looked up. An uncle looked up. A cousin looked up. Someone said, ‘You can sure tell who the pilots are in this family!’ ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [February 25, 2006, 2:02am UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/17 "2006-02-25T02:02:19Z")
> [@jali](#): > > Could my eyes be playing tricks? Perhaps the altitude differs by more than I’m thinking. Please clear this up for me - I don’t smoke inside my home, so I’m outside looking at airplanes on a regular basis and it’s starting to bug me. They will have been at different altitudes. Your human brain is not very good at judging altitude. There is no known size reference to compare the aircraft to. And one airliner may be literally twice the size of another so it is even difficult to tell relative altitude. **RickJay** , there were some bombers that flew that high. The B17 had a service ceiling over 35,000’. ---
**Author:** ![jali](https://avatars.discourse-cdn.com/v4/letter/j/ecae2f/32.png) [@jali](https://boards.straightdope.com/u/jali)\ **Post date:** [February 25, 2006, 5:46pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/18 "2006-02-25T17:46:31Z")
You guys are the bomb! The responses here are the reason I joined. Thanks all. ---
**Author:** ![KCB615](https://avatars.discourse-cdn.com/v4/letter/k/ea666f/32.png) [@KCB615](https://boards.straightdope.com/u/KCB615)\ **Post date:** [February 25, 2006, 8:33pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/19 "2006-02-25T20:33:28Z")
> [@](#): > > You guys are the bomb! Things not to say when talking about aircraft… ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [February 25, 2006, 10:11pm UTC](https://boards.straightdope.com/t/airplane-smoke-trail/345957/20 "2006-02-25T22:11:56Z")
Some early jet aircraft had engines that left a smoke trail, though. [Next page](https://boards.straightdope.com/t/airplane-smoke-trail/345957.md?page=2)