dailynewsnblog
A 
United Airlines passenger has taken to the internet to recount their experience of listening in on cockpit communications during a recent domestic flight. The individual was tuned in to the airline’s beloved “Channel 9,” which allows passengers to listen in to real-time conversations between the cockpit and air traffic control (ATC).
However, on this occasion, the channel was broadcasting more than just ATC audio — the passenger could also hear everything spoken in the cockpit itself between pilots, which apparently included “a few curse words.” It seems the flight crew accidentally switched on (or forgot to turn off) elements of the panel controlling audio output, allowing passengers to hear their conversations for the entire flight.
Passenger Listens In On Everything In United Cockpit
In a post on Reddit, user ‘UncleMcBubba’ shared details of an unusual experience onboard a United flight out of 
Denver International Airport (DEN) last week. While tuned in to the flight’s Channel 9 audio feed — now listed as ‘From The Flight Deck’ on United’s in-flight entertainment (IFE) system — the passenger was surprised to learn that they could also hear everything the pilots were saying to each other.
This was available for the entire flight, with the user claiming they listened to the two pilots “talk to each other about their lives” and other subjects for over two hours. The not-so-sterile cockpit chatter also included the odd moment of foul language, with the two pilots apparently unaware their words were being broadcast on the audio channel. Although they did not specify their destination, the passenger confirmed it occurred on an Airbus A319. They added on Reddit,
“I listened to all the calls, prechecks, and the pilot and copilot talk to each other about their lives, kids, random terrain we were flying over, previous incidents they’ve encountered that may or may not have gone unreported, and even dropping a few curse words during the flight.”
What Is Channel 9?
One of the fun features United has included on its aircraft for decades is an audio channel broadcasting communications between the flight deck and ATC. This was initially known as Channel 9, as it was the ninth dial on the airline’s former audio system, before United renamed it to From The Flight Deck.
The feature was pretty universal on United flights in previous decades, but is now usually switched off unless a request is made to turn it on. It can now be accessed through the airline’s IFE system under the Audio section — ordinarily, if the feature has been enabled for the flight, it will allow passengers to listen in on ATC communications only. So, how exactly was this passenger able to hear everything else?
On an Airbus plane, Channel 9’s audio feed is managed by an observer audio control panel (ACP), and pilots can toggle which audio channels are fed through it and broadcast to passengers. The most likely explanation is that all channels were enabled on a previous flight, and the pilots simply didn’t notice or forgot to turn them off.
FAA Mandates 25-Hour Cockpit Audio Despite Pilot Surveillance Fears
This is the latest move being made to improve air safety.
How Sterile Is The Cockpit?
Pilots are expected to adhere to the concept of a ‘sterile cockpit’—which means avoiding unnecessary talking or activities during flights — particularly during the most important phases. It mostly comes into play at 10,000 feet or below, the idea being to ensure pilots are not distracted by trivial matters.
When the aircraft is at cruising altitude, it is less imperative to maintain a sterile cockpit, as the concept was primarily designed for the most critical phases of flight, when pilots need to be at their most attentive. While we don’t know for sure if the chit-chat persisted during the takeoff or landing phase, pilots are generally very strict about maintaining a sterile cockpit during these phases.
