Let’s unpack what makes a series take flight.

And maybe fewer of us would associate the word with that tiny eternal flame in our gas stove.

But how did the term become associated with television?

Pilot Episode Explainer

From top left to bottom right: ‘Friends’; ‘The Big Bang Theory’; ‘The Golden Girls’; ‘Seinfeld’.Credit:Warner Bros. / Courtesy Everett; Robert Voets/CBS; Castle Rock Entertainment / Courtesy Everett; Herb Ball/NBCU Photo Bank

Here, let us be your pilot through the world of TV pilots.

What is a pilot?

But most of the time, a pilot gives a potential show a screen test to determine its viability.

Happy Days - “Reluctantly Aggressive” - Season One - Pilot - November 26, 1973 Kathy O’Dare, Ron Howard

ABC Photo Archives/Disney General Entertainment Content via Getty

Why are the first episodes called pilots?

(Serenitywas later the title of the2005 film continuationofFirefly.)

What are some different types of pilots?

SEINFELD, from left: Jerry Seinfeld, Jason Alexander, ‘The Seinfeld Chronicles’, aka ‘Pilot’, aka ‘Good News, Bad News’, (Season 1, episode 101, aired April 5, 1989)

Castle Rock Entertainment / Courtesy Everett

Jesse Grant/Getty

Not all pilots function as first-off iterations of new series.

TheCSIandNCISfranchises are particularly well-known for using pre-existing series to launch new franchise installments.

His character later helmed the web connection’s seriesThe Soul Man(20122016).

Betty White, Georgia Engel, Jane Leeves, Dave Foley, Constance Zimmer, David Starzyk and Cedric the Entertainer appear onstage during “Hot In Cleveland” LIVE! at the CBS Studio Center on March 26, 2014 in Studio City, California.

From left to right: Betty White, Georgia Engel, Jane Leeves, Dave Foley, Constance Zimmer, David Starzyk, and Cedric the Entertainer.Jesse Grant/Getty

Do all pilots function as the first episode?

Universal/Courtesy Everett

Not all pilots function as first episodes, although thats rare.

One unique example isHappy Days, which never had its own dedicated pilot.

MULHOLLAND DRIVE, Naomi Watts, Laura Harring, 2001,

Naomi Watts, Laura Elena Harring.Universal/Courtesy Everett

The series notably launched two successful backdoor pilots of its own:Laverne & ShirleyandMork & Mindy.

Then there’s the originalStar Trekseries (1966-1969), which shot two pilots.

There are also cases of pilot episodes ending up in cinemas.

A recut version hit American box offices the following year.

It remains one of thelate director’s most celebrated pictures.