Have you seen the images some pilots take from the cockpit?

Remarkable, mind-boggling, fantastic. Cities spread out below, their streets and railways pumping like arteries, or countryside, green and lush, stretching for miles and miles, stopping only at the horizon.

A post shared by @airguide on May 15, 2017 at 11:21am PDT

But these are all taken above at least 10,000 feet. In fact, pilots are barely allowed to talk to each other if the aircraft is below this altitude. And this is thanks to something called the Sterile Cockpit Rule.

What is the Sterile Cockpit Rule?

It means that during take-off and landing - before the aircraft passes 10,000 feet on ascent and after it has passed 10,000 feet on the approach - pilots must focus entirely on “their essential operational activities” and “avoid non-essential conversations”.

“Sterile flight deck procedures are meant to increase the flight crew members’ attention to their essential operational activities when their focused alert is needed,” reads the code, which applies to all aviation authorities in the EU, including the British Civil Aviation Authority (CAA).

Where did the rule come from?

The regulation began life in the US in 1974 in response to the crash of Eastern Air Lines Flight 212, which fell just short of the runway at Charlotte Douglas International in heavy fog, with the loss of 72 lives.

Despite the poor visibility, investigators determined that the cause of the crash was in part due to “the flight crew’s lack of altitude awareness at critical points during the approach due to poor cockpit discipline”. The National Transportation Safety Board (NTSB) found that during the approach the crew were engaged in “non-pertinent” conversation on topics ranging from “politics to used cars”, and found that this would have been distracting enough for the pilots to fail to check their instruments properly in a situation when they were relying on them to land safely.

As the pilots tried to visually locate Charlotte Airport, they were distracted by attempting to spot the nearby Carowinds Amusement Park tower

It further found that as the pilots attempted to visually locate Charlotte Airport, they were distracted by attempting to spot the nearby Carowinds Amusement Park tower. During the descent the captain did not make any of the necessary altitude callouts, adding to the lack of altitude awareness.

Seven years later the Federal Aviation Administration introduced the Sterile Cockpit Rule amid concerns that the growing automation and comfort of flight decks created an office environment in which pilots were more likely to lose concentration and have a good natter.

The tower at the Carowinds theme park in Charlotte Credit: ALAMY

The rule, which all airlines are required to enforce, forbids “any duties during a critical phase of flight except those duties required for the safe operation of the aircraft”, citing as example, calls for galley supplies, confirming passenger connections, or airline promotions over the tannoy.

It also bans flight crew members or pilots from “eating meals, engaging in nonessential conversations… and nonessentials communications between the cabin and cockpit crews, and reading publications not related to the proper conduct of the flight”. It states this rule applies below 10,000 feet, and during taxi, take-off and landing.

But what if there's an emergency in the cabin?

This has been one of the downsides of the rule. There has been reported confusion as to when exactly flight attendants should break their silence because of the Sterile Cockpit Rule. The FAA noted: “Hesitancy or reluctance on the part of a flight attendant to contact the flight crew members with important safety information because of a misconception of the sterile cockpit rule is potentially even more serious than the unnecessary distraction caused by needless violations of the sterile cockpit.”

Indeed in 1995, a flight attendant watched a passenger door seal separate just after take-off but did not contact the pilot because of the rule of silence.

Japan Airlines, in order to avoid any confusion, listed the instances when flight attendants should contact the cockpit below 10,000 feet.