Pilots and experts are trained to be attentive on planes, so even when they don't have to fly the plane and can sit in the main cabin, pilots notice things that other passengers don't. Business Insider interviewed two airline pilots and collected responses from a Quora thread to find out what they notice when they're flying in the main cabin.
1. The angle of the light that comes through a cabin window
Experienced pilots know that a sudden change in the angle of the light that comes through a cabin window can be the first sign that the pilot is changing course. "An unexpected, significant shift in the angle of the Sun can be your first sign that a course change is being made," Farrier wrote.
Many air travelers don't expect clear and timely explanations when their flight is delayed, but they should, according to Patrick Smith, a pilot and author of the air travel blog Ask the Pilot. "It's always something that everybody can understand if you just use the right language and are patient enough and timely enough with it," Smith said.
3. Landing routine
"Most passengers don’t notice the level-off that often occurs when the airplane is about to enter the approach environment or descend below 10,000 feet," Hachi Ko wrote on Quora. "When I feel that little level-off for the airplane to slow, I imagine the pilots going through the checklist, and at the right time, I turn to my companion and go 'Ding!' I'm within 4 or 5 seconds well over 50% of the time and it freaks them out."
4. Emergency exits
Many passengers tune out during safety briefings, but pilots understand how important they can be. In the event of a crash landing, you might not have the time or ability to figure out where the exits are.
5. Suspicious scents
Scents can be one of the strongest indicators that something's wrong on a plane, as they can quickly hint at problems with the engine or fuel-storage systems.