Most people vent about bad days or breakups in their journals. Leonardo da Vinci used his to dream up human flying machines, centuries before the first aircraft was developed.

This month, da Vinci’s 500-year-old “Codex on the Flight of Birds” makes a rare visit to the States. In the notebook, on display at the National Air and Space Museum through Oct. 22, the original Renaissance man explores the principles of bird flight and how they could be adapted to make flying machines.

Da Vinci became interested in flight while designing equipment for the Italian military. “It really became an obsession for him,” says Peter Jakab, chief curator at the Air and Space Museum.

According to Jakab, the codex was created around 1505, near the time da Vinci was painting his masterpiece, the “Mona Lisa.” After da Vinci’s death, his notebooks were largely lost to the public until their rediscovery in the 19th century.

In addition to viewing the actual codex in a display case, visitors can virtually leaf through all 18 “folios” (two-sided pages) of the notebook at interactive stations. The codex is fittingly housed with the museum’s “The Wright Brothers & The Invention of the Aerial Age” exhibition, which includes the first successful powered aircraft — the brothers’ 1903 flyer.

The codex, on loan from the Biblioteca Reale in Turin, Italy, rarely leaves its home. “This’ll be a rare opportunity,” Jakab says.

1: Most scholars say Leonardo da Vinci wrote in a so-called mirror script because he was left-handed and didn’t want to smear ink across the page. The language here is (backward) Italian.

2: Through text and sketches, da Vinci explored the possibility of flying machines by studying birds. Here, he drew a bird suspended from an apparatus, and discusses how the movement of air over the surface of the bird’s wing affects its lift and control. Da Vinci had a rudimentary concept of gravity before it was formally described by Sir Isaac Newton in 1687, curator Peter Jakab says.

3. Da Vinci explored how a pilot might shift his body position in an aircraft to balance it.

4: Da Vinci envisioned a mechanical structure that would replicate the movement of a bird’s wing.

5: Da Vinci continued to analyze how air flowing over a bird’s wing affected its balance.

National Air and Space Museum, Independence Avenue at S Street SW; through Oct. 22, free; 202-633-2214. (L’Enfant Plaza)