Concorde remains one of the most recognizable aircraft ever built, but one of its most unusual moments came in 1996 when Air France temporarily repainted one of its supersonic jets in Pepsi’s deep blue promotional livery. The aircraft looked spectacular on the ground, yet the eye-catching design hid a serious aerodynamic and thermal problem: the darker paint made the jet operate at higher temperatures during supersonic flight.

This raised a practical question that still fascinates aviation fans today. Why would simply changing the color of Concorde’s paint cause enough technical issues that engineers had to limit speed, route choices, and even how long the aircraft could remain at high Mach?

To answer that, we need to examine how Concorde managed heat, why color mattered at fifty thousand feet, and what exactly happened to Air France’s Pepsi-branded aircraft during its brief two-week career in blue paint.

Thermal Sensitivity At Twice The Speed Of Sound

The short answer is that dark blue paint absorbed more heat from sunlight and increased the temperature of Concorde’s outer skin. Concorde already operated near its thermal limits because flying at Mach 2 created significant aerodynamic heating. The additional heat from the darker paint reduced the safety margin built into the airframe and forced Air France engineers to impose operating restrictions.

In practice, this meant limiting the aircraft to Mach 1.7 instead of Concorde’s normal Mach 2.02 – Mach 2.04, and capping the time spent above Mach 2 to about 20 minutes. At higher temperatures, the fuel inside the wings would heat to a level engineers were not comfortable with. The aluminum structure also expanded more than intended, which affected fatigue margins and inspection requirements.

From an engineering perspective, the campaign highlighted how carefully Concorde’s designers controlled thermal loads. Something as simple as paint color could directly influence the safe operating speed. That level of sensitivity was unusual among commercial aircraft, but it was a direct consequence of flying through the stratosphere at more than twice the speed of sound.

Physics Behind Concorde’s Heat Limits

The Pepsi Concorde was a marketing idea that was part of a $500m campaign that ended up creating more engineering headaches than publicity value. The problem came down to physics. The Concorde already operated right at the edge of what aluminum could tolerate during sustained supersonic flight. At around Mach 2, the skin temperature of the jet could climb above 260°F (about 127°C).

Many factors combined to make paint color unusually important on Concorde. These include solar heating, aerodynamic heating, material limits, and the specific reflectivity properties of the aircraft’s standard paint. Basically, the color choice was dictated by the laws of physics.

• Solar radiation and color absorption: We all know that dark colors absorb more solar radiation than light colors. For example, on a hot sunny day, a black car becomes hotter than a white one. The same principle works for airplanes. A deep blue surface under sunlight can heat tens of degrees hotter than a white one. On conventional airliners that operate at subsonic speeds and lower altitudes, the margin is generous, and the structure is not close to thermal limits. Concorde was different. The aircraft operated above 50,000 feet (15,240 meters), where the sun’s intensity is higher and atmospheric filtering is reduced. At those altitudes, the paint’s reflectivity was a thermal control tool rather than a simple cosmetic matter. White paint minimized solar heating, reflecting a portion of it, helping the aircraft stay within temperature limits set by its aluminum skin.
• Aerodynamic heating at supersonic speed: At Mach 2, the aircraft’s skin heats due to the compression of air molecules against the fuselage and wings. This is a direct function of speed, and it can be estimated using well-understood aerodynamic heating equations. For the Concorde, the forward fuselage and wing leading edges reached the highest temperatures. Operating at Mach 1.7 generated less aerodynamic heating than Mach 2. Engineers calculated that flying at Mach 1.7 instead of Mach 2.0 would keep the Concorde within its thermal envelope.
• Material expansion limits: Concorde used conventional aluminum alloys for most of its structure. Aluminum handles moderate heat but begins to lose strength as temperatures rise. The aircraft design team set strict maximum allowable skin temperatures. If the temperature rose beyond those limits, expansion would exceed what the structure and joints could safely tolerate.

The Pepsi aircraft retained white paint on the wings and forward fuselage, which were the areas exposed to the highest heating. The tail and portions of the rear fuselage were blue. Even then, testing showed that the temperature margin at Mach 2.0 would be too small.

Balancing Branding Goals With Thermal Safety

After a promotional press conference, which was attended by VIPs like Andre Agassi, Cindy Crawford, and Claudia Schiffer, the Concorde F-BTSD “Sierra Delta” embarked on a ten-day publicity tour across Europe and the Middle East, flying 16 legs to 10 cities in two distinct phases.

In the first phase, from March 31 to April 4, the aircraft was crewed by Captain Y. Pecresse, First Officer B. Bachelet, and Flight Engineer A. Piccinini. The routes covered Paris, London, Dublin Airportand Stockholm Arlanda Airport.

The second phase, from April 6 to April 9, was flown by Captain G. Arondel, First Officer P. Decamps, and Flight Engineer M. Suand. It continued the tour from Paris CDG to Beirut–Rafic Hariri International Airport, Dubai International Airport, Jeddah Airport, Cairo International Airport, Milan Linate Airport and Madrid Barajas Airport before returning to Paris Orly Airport. After completing the 16 promotional flights, the aircraft reverted to its standard Air France livery, and it is now on display at the Musée de l’Air et de l’Espace at Paris-Le Bourget Airport.

The aircraft had to meet Pepsi’s branding goals while staying inside strict operational limits. The solution was a careful compromise. Engineers applied blue only where temperatures were lowest, the routes were shortened compared to the transatlantic ones, and the airline restricted high-speed flights to avoid exceeding the thermal envelope.

For Air France, the project was unusual but manageable. No long-term structural impact was reported, but only because the aircraft never pushed beyond Mach 1.7 while wearing the special livery. The limits, however, did not prevent Air France from realizing a brilliant special color in 1989 to celebrate the bicentennial of the French Revolution, and to mark the 20 years since the Concorde’s maiden flight.

Thermal Vs. Aerodynamic Constraints

Some people assume the problem was aesthetic rather than technical, or that the blue paint created aerodynamic drag. Others suggest the aircraft could have flown at Mach 2.0 anyway, because aluminum can tolerate brief temperature spikes. These explanations do not match the engineering data.

The issue was mainly thermal. Reflectivity matters far more at Mach 2 than it does on conventional jets. The main constraint was heat absorption from solar radiation and how that affected the aircraft’s limited thermal margin. A darker livery would not have created significant drag, and the shape of Concorde did not change because of the paint.

Compared with other high-performance aircraft, Concorde operated with a much tighter thermal margin. The Pepsi case illustrates how sensitive the aircraft was to external coatings compared with other supersonic designs.

Why Do Military Supersonic Aircraft Wear Unusual Liveries?

This question comes up almost every time the Pepsi Concorde story is told. If Concorde needed to stay white to stay cool, why do we see military aircraft painted in charcoal grey, desert brown, or even black? A short answer could be that military jets experience a very different thermal environment, but it’s with the long answer that things get interesting!

The biggest distinction is how long each aircraft stays above the sound barrier. Concorde cruised at Mach 2 for up to three hours. Fighters do not operate that way. Most frontline jets spend only brief periods above Mach 1.5 or Mach 2, often a handful of seconds to a few minutes. They accelerate, perform the required maneuver, then throttle back. The thermal spike is sharp, but it is short, so the paint simply doesn’t remain hot long enough to overwhelm the structure beneath it.

The F-15C and F-16C, both capable of touching Mach 2, typically cruise at subsonic speed to conserve fuel, and only go supersonic when required. Their standard gray schemes are chosen for visual camouflage and radar scattering, not heat management.

The MiG-31 Foxhound, which can sustain higher speeds than most Western fighters, is painted in various greys and blues because its operational time at high Mach is still far shorter than a Concorde transatlantic crossing.

Then another question arises: how come the Mach 3-capable SR-71 Blackbird was totally black? That’s not a contradiction: the Blackbird was painted black not because the black paint runs cool, but because the aircraft’s titanium skin was designed to operate at temperatures far beyond Concorde’s aluminum structure.

At Mach 3, the SR 71’s surface temperature could exceed 900°F (482°C) from aerodynamic heating alone, far exceeding any heat gained from sunlight. At those extremes, emissivity becomes crucial, and black coatings radiate heat away far more efficiently than lighter colors. The iron-infused black paint helped the Blackbird shed thermal energy, reduce hotspots, and keep the skin temperature stable during brief but intense supersonic dashes. And the aircraft’s materials, joints, and fuel system were custom-engineered for that harsh environment.

Concorde’s Blue Livery: A Lesson In Supersonic Engineering

The Pepsi blue livery created issues for Concorde because it absorbed much more heat than the standard white paint. At supersonic speed, that extra heat pushed the aircraft close to or beyond its approved temperature limit. The simplest and safest solution was to restrict the promotional aircraft to Mach 1.7 until the livery was removed.

The case remains one of the most unusual intersections of commercial branding and high-performance engineering in civil aviation. It shows how carefully Concorde’s designers and operators managed heat, and how even small changes could have measurable effects on performance.

Looking back, the Pepsi Concorde has become a popular piece of aviation history. For many fans, it is a reminder that Concorde was a highly specialized machine with unique requirements. The blue livery may have been short-lived, but it offered the public a rare glimpse into the complex engineering behind the world’s only successful supersonic airliner.