Dual 3.5mm Male to 3.5mm Female AUX Audio Jack Adapter
AMZER Dual 3.5mm Male to 3.5mm Female AUX Audio Jack Adapter Converter for Using Headphone on Airplane Airline Flight - Walmart.com
Bose® QuietComfort® headphones airline adapter
Airfly Pro Plug Airplane Headphone Adapter, 3.5mm Dual Stereo Jack Male to Female Airline Headset Adapter Plug for Mobile Phone Headset Speaker Conversion Head Audio Compatible with Sony Headphones - Walmart.com
Ten minute hacks: Hacking airplane headphones | The Technical Blog of James