# contrails and 9/11 **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [February 22, 2019, 8:26pm UTC](https://boards.straightdope.com/t/contrails-and-9-11/830043 "2019-02-22T20:26:11Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [February 22, 2019, 8:26pm UTC](https://boards.straightdope.com/t/contrails-and-9-11/830043/1 "2019-02-22T20:26:11Z")
> **[Are jet contrails the latest threat?](https://www.straightdope.com/columns/read/2556/are-jet-contrails-the-latest-threat/)** Is it true that after Sept. 11 2001, the USA had bright clear skies _because the passenger jets were grounded_? ---
**Author:** ![GreysonCarlisle](https://avatars.discourse-cdn.com/v4/letter/g/a87d85/32.png) [@GreysonCarlisle](https://boards.straightdope.com/u/GreysonCarlisle)\ **Post date:** [February 22, 2019, 8:50pm UTC](https://boards.straightdope.com/t/contrails-and-9-11/830043/2 "2019-02-22T20:50:04Z")
[Here’s an article](https://www.nature.com/news/2008/081231/full/news.2008.1335.html) from _Nature_ that explores the climate effects of the 9/11 grounding. > [@](#): > > Absent contrails were never assumed to be the sole cause of the large temperature ranges, he emphasizes. “We’ve always said it’s a combination of the lack of airplanes and the natural weather conditions,” he says. ---
**Author:** ![Uncle\_Jocko](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uncle_jocko/32/2932_2.png) [@Uncle\_Jocko](https://boards.straightdope.com/u/Uncle_Jocko)\ **Post date:** [February 25, 2019, 3:55am UTC](https://boards.straightdope.com/t/contrails-and-9-11/830043/3 "2019-02-25T03:55:33Z")
We had bright clear skies _on_ September 11, too, _before_ the planes were grounded.