Why the earphone on plane are mostly two pins instead of one?

Here’s the real reason why most airplane headphones still have two pins (dual-prong) instead of the usual single 3.5 mm jack:

1. Historical safety rule (the original reason)

   Back in the 1960s–1980s, aviation regulators (mainly the FAA) were worried that passengers wearing high-quality noise-canceling or tightly sealed headphones might not hear emergency announcements or crew instructions during evacuation.  

   So they required in-flight entertainment systems to use a non-standard dual-pin plug. Regular consumer headphones with a single pin simply couldn’t be plugged in, forcing people to use the cheap airline-supplied ones (which were usually low-quality and had almost no noise isolation). That way you’d still hear the crew yelling “Unfasten your seatbelts and get out!”

2. Two separate pins = left & right channel redundancy  

   One pin carries the left channel, the other the right. If one pin or wire breaks, you still get mono sound instead of total silence (a tiny safety/quality bonus).

3. It makes airlines extra money  

   Because your own headphones don’t fit, you’re more likely to:  

   - Buy the airline’s overpriced earbuds on board (often US$5–20)  

   - Buy an adapter in the airport shop or duty-free catalog  

   That’s pure profit, so many airlines are in no rush to switch.

4. Old airplanes, old systems  

   Thousands of older aircraft (A320s, 737s, 777s built before ~2015) still have the original dual-pin sockets wired into every seat. Retrofitting them to single 3.5 mm or USB-C/Bluetooth costs millions, so they keep the old system.

Good news: Newer planes (A350, 787, A220, many new A320neo/737 MAX) and premium cabins on long-haul flights are rapidly switching to standard single 3.5 mm, USB-C, or Bluetooth. But on most older or budget-carrier planes, the infamous two-pin headphone jack is still alive and well.

Pro tip: Bring a cheap airplane headphone adapter (looks like a tiny Y-shaped splitter, costs $2–8 online or at any airport). Then you can use your own AirPods Pro, Sony XM5, Bose, etc., and enjoy the flight like a human being.