Newer passenger airplanes use the familiar 3.5mm jack but if you travel a lot you probably have noticed two-prong 3.5mm jacks on some passenger airplanes. One might ask, why do some airplanes use two prong headphones?
The story behind airplanes with two prong headphones is actually an interesting one because airplanes with two-prong headphone jacks have been around since at least the 1960s, before the 3.5 mm headphone jack became hugely popular in the 1980s when Sony released the Walkman.
If you flew or know someone who flew on an airplane during the 1970s they will tell you that airplanes back then used a pneumatic headphone design built-in to the armrests which required two separate prongs to deliver acoustic sound waves to the left ear and right ear.
At the time, airline pneumatic headphones were rented out to airline passengers, but then became obsolete in the 1990s being replaced with two-prong electrical headphones. But why use two-prongs?
As the story goes, airlines continued designing their fleets with two-prong headphone jacks to deter passengers stealing airline headphones. This is interesting because most airlines today charge for airline headphones, when just 10 years ago airlines allowed passengers to keep them for free (at least some did).
If you happen to be flying in an airplane that uses two-prong headphones and want to use your own Bluetooth headphones, you'll need a Bluetooth airline double prong headphone adapter such as the KitSound Bluetooth airplane adaptor, which is a tiny Bluetooth transmitter with two headphone prongs that plug into the airplane headphone socket, allowing your Bluetooth headphones to receive signal.