Pi written out in the sky over Austin in 2014. Credit: AirSign |

Those still lingering at the South by Southwest festival in Austin on Thursday (March 13) may have noticed a string of numbers emerging in the sky.

On the eve of Pi Day (which is Friday, March 14), five synchronized aircraft wrote out the first few hundred digits in pi's infinite sequence.

Starting with the famous 3.14, the dot matrix-style numbers went on for miles, according to AirSign, the company that organized the "Pi in the Sky" stunt, which started at 6:28 p.m.

"We chose 6:28 because it's pi times two, a number some believe is the truer reflection of the power of the circle," company officials wrote in a blog post.

Pi, or π, is a mathematical constant that represents the ratio of a circle's circumference to its diameter (π = c/d). No matter the size of the circle, pi remains the same. Because pi is an irrational number, it cannot be expressed as a simple fraction. Rather, pi can be written as an infinite decimal that never repeats (3.14159…). By December 2013, computers had calculated pi to a record 12 trillion digits, according to Numberworld.org.

Pi multiplied by two (6.28318...) is called tau and it is defined as the ratio of a circle's circumference to its radius. Some mathemeticians have argued that tau would be more useful as a mathematical constant as it appears more often in calculations.

```
```
Planes writing numbers in the sky with their jet stream. #piinthesky awesome. Thanks @airsignusa pic.twitter.com/xEWuwbUb8Q

— Keri Lewis Brown (@kerilewisbrown) March 14, 2014

```
```
I don't always instagram pictures of the sky, but when I do, it's because they're sky writing pi. #piinthesky pic.twitter.com/DBzVANz9H8

— Sarah Dieken (@SarahDieken) March 14, 2014

*Follow Megan Gannon on **Twitter** and **Google+.* *Follow us **@livescience**, **Facebook* *& **Google+**. Original article on **Live Science.*