White Spots Over the Atlantic: Clouds, Not Mystery

Those brilliant white specks and streaks visible from an airplane window over the Atlantic? Overwhelmingly, they're clouds—not foam, not algae, not unknown phenomena. Here's what you're actually seeing.

Cloud Types from Above

• Cumulus: "Cotton balls" — fair-weather, low (2,000–6,000 ft), scattered or clustered. Indicate stable air.
• Stratus/Stratocumulus: Gray-white blankets or rolls — low, layered, often cover vast areas. Overcast makers.
• Cirrus: "Mare's tails" — wispy, high (20,000–40,000 ft), ice crystals. Often precede weather changes.
• Cumulonimbus: Thunderstorm towers — anvil tops at 40,000–60,000 ft. Avoid!
• Altocumulus: Mid-level (6,500–20,000 ft) — rippled sheets or patches, "mackerel sky."

Why They Look So White

Clouds are countless tiny water droplets or ice crystals. They scatter all visible wavelengths equally (Mie scattering) → pure white. Thicker clouds appear brighter; thin ones let blue sky through.

Non-Cloud White Spots

• Sun glint: Specular reflection off calm water — bright, moving, mirror-like.
• Ship wakes: White trails from propeller turbulence + bubbles — linear, persistent.
• Whitecaps: Wind-driven foam on wave crests — textured, widespread at >15 kts wind.
• Sea ice / icebergs: High latitudes — geometric, stationary relative to clouds.

Identification Tips

• Motion: Clouds move with wind aloft (often different from surface). Ship wakes move with ship.
• Texture: Clouds = soft/feathery/cauliflower. Whitecaps = granular. Sun glint = mirror.
• Shadow: Clouds cast shadows on lower clouds/sea. Sun glint doesn't.
• Altitude context: Cirrus = high, cold. Cumulus = low, warm.

Next flight, you're not seeing mysteries—you're reading the atmospheric textbook written in water and light.