Only 24 years elapsed between the Wright brothers' first powered flight on December 17, 1903, and Charles Lindbergh's first Atlantic crossing with his single-engine "Spirit of St. Louis" in 1927. A similar transformation occurred in horology within two decades as timepieces migrated from the vest pocket to the wrist. And there's another common denominator between the aviators and watchmakers. As was the case aboard ships in the 18th century, aviators also relied on timekeeping instruments for navigation. Philip van Horn Weems came up with the idea for an hour angle watch which, enhanced according to suggestions by Charles Lindbergh, would allow simpler, faster, and more precise positioning when used together with a sextant and a radio signal. Two particularly noteworthy exemplars of such hour-angle – or siderometer – wristwatches were developed by Patek Philippe and are now both on display at the Patek Philippe Museum.

Rather than being an hour-angle watch - that became obsolete with the advent of GPS navigation -  Patek Philippe's Ref. 5524 Calatrava Pilot Travel Time is a timekeeping instrument with a time-zone function that is especially useful in air travel.

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Patek Philippe's Ref. 5524 Calatrava Pilot Travel Time is a decidedly masculine watch that aptly symbolizes the conquest of the skies by aircraft and the conquest of the wrist by wristwatches. © Patek Philippe

For nearly eighty years, Patek Philippe time-zone watches have adhered to this principle in a unique way. In the 1930s, together with gifted watchmaker Louis Cottier, the manufacture developed its first "Heure Universelle" (World Time) wristwatches. The first patent for the meanwhile legendary Travel Time mechanism was granted to Patek Philippe in 1959. It was extremely simple to operate and simultaneously displayed the time in two different time zones.
Patek Philippe refined the two-time-zone mechanism to a new level of perfection. When the local-time hour hand is moved forward or backward in one-hour increments, an isolator uncouples the time-zone mechanism from the going train. This prevents the degradation of the amplitude of the balance and allows it to continue oscillating at a regular rate. The advantage: the watch continues to run with the accustomed accuracy.

In the new Ref. 5524 Calatrava Pilot Travel Time, this advanced mechanism is part of the self-winding caliber 324 S C FUS manufacture movement with a sweep seconds hand, an analog date, and a heavy central rotor in 21K gold. Like the time-zone mechanism, this movement is superbly finished. The Spiromax® spring that breathes in the Gyromax® balance is made of Silinvar®, a derivative of silicon. The special properties of this material, combined with the geometry patented by Patek Philippe, assure high dependability as well as the rate accuracy tolerance of -3/+2 seconds per day as specified by the Patek Philippe Seal.

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The automatic calibre 324 SC FUS: 294 components and max. 45 hours power reserve. © Patek Philippe

The blue dial resembles the body paint of American fighter planes in the 1930s. Thanks to large applied Arabic numerals in white gold and broad baton-style steel hands with Superluminova coatings, the local time is easily and clearly legible, both during the day and at night. In the typical Travel Time style, the home-time hour hand is skeletonized and remains discreetly in the background. A separate day/night indicator is assigned to both time zones (at 9 o'clock for local time and at 3 o'clock for home time). The analog date at 6 o'clock is totally new: it displays the date in 3-day increments.

The sleek classic face of the Calatrava Pilot Travel Time is framed by a large-format 42-millimeter white-gold Calatrava-style case. Its bezel is flat and slightly inclined; the caseband merges elegantly with the lugs that secure the strap bars. The crown and the two time-zone pushers are fluted. Additionally, the time-zone pushers are equipped with a patent-pending safety lock that prevents unintended adjustments of the local time setting.

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The sapphire-crystal display back reveals beautiful details such as the chamfered bridges with Geneva striping, the circular-grained gold rotor with perlage in the center, snailed flanks, and a Calatrava cross. © Patek Philippe

The strap is crafted from vintage brown calfskin with contrast topstitching and recalls the leather belts that belonged to a classic pilot's gear. The white-gold clevis prong buckle was inspired by the harnesses worn by pilots to keep their survival kits and parachutes readily deployable without hampering their freedom of movement.