Romantic Flight (also called Astrid's theme) is a musical piece composed by John Powell. It was first featured in How to Train Your Dragon film and is most notable during Hiccup and Astrid's first flight scene.
This theme was specifically made for Astrid's character and reprises during most of her emotional and heartfelt scenes on both the show and in the movies.
Scenes that feature Astrid's theme
- When Astrid is first introduced by Hiccup while she is walking towards him in slow motion in a ball of fire
- During the Romantic Flight sequence.
- The first time Astrid kisses Hiccup on the cheek in The Cove.
- The first time Astrid officially kisses Hiccup at the end of the first movie.
- During Dragon Racing in the second movie when Astrid's character is reintroduced.
- During Astrid's scene on Itchy Armpit when Hiccup tells her she knows exactly who she is.
- When Astrid kidnaps Eret.
- When Hiccup kisses Astrid for the first time at the end of the second movie.
Episodes that feature Astrid's Theme
- Fright of Passage when Hiccup holds a speech on Astrid's behalf at the end of the episode.
- Free Scauldy when Astrid pretends to flirt with Snotlout to get him off her back.
- Gone Gustav Gone when Gustav daydreams about Astrid.
- Have Dragon Will Travel, Part 2 when Astrid shares an emotional moment with Hiccup at the end of the episode.
- Team Astrid when Astrid is walking by herself in the dark, leading up to a heartfelt moment with Stoick the Vast.
- Night of the Hunters, Part 2 when Astrid reunites with Stormfly.
- At the end of Buffalord Soldier when Astrid thanks Hiccup for doing what he did for her, and he says that she would have done the same for her, with Astrid replying "I can't imagine a world without you in it either."
- For a brief moment in Last Auction Heroes when Astrid places her hand on Hiccup's shoulder and he responds by placing his hand on top of hers.
- Defenders of the Wing, Part 1 when Heather is helping Astrid walk after she got shot in the leg by a hunter's arrow.
- In Blindsided, when Hiccup comforts Astrid after she says she feels helpless.
- At the end when Hiccup and Astrid are talking about why Hiccup did not kiss her when he had the opportunity, followed by them sharing their first kiss as a couple.
- According to Bonnie Arnold, the producer of the How to Train Your Dragon trilogy, Romantic Flight is actually called "Astrid's Theme." 
- There are a few rare times Astrid's theme is burrowed to other characters such as Ruffnut when she falls in love with Eret, or during Stoick's first flight with Hiccup on the old Cartoon Network show.