Here is a concise summary of the text:
**5 Hidden Features on Airplanes Revealed**
1. **Triangular Stickers**: Indicate specific windows for flight crew to check wings for ice or malfunctioning flaps.
2. **Hidden Sleeping Compartments**: Small, often windowless rooms for exhausted crew to rest, usually above first class.
3. **Loops on Wings**: Yellow loops on Airbus planes serve as anchors for emergency escape ropes to prevent slipping on wet wings.
4. **Holes in Windows**: Tiny "breather holes" in the middle pane of triple-layered windows to equalize pressure and prevent glass failure.
5. **Adjustable Armrest Button**: A hidden button on aisle seats allows passengers to move the armrest out of the way, increasing legroom and accessibility.
Here are the key facts extracted from the text, numbered and in short sentences, without opinions:
**Section 1: Triangular Stickers on Plane Windows**
1. Only four windows on each plane are marked with a triangular sticker.
2. The stickers are usually red or black and align with the front and back edges of the aircraft's wings.
3. The stickers indicate which windows flight attendants should look through to check the wings.
**Section 2: Hidden Sleeping Compartments**
4. Some airliners feature hidden compartments for the crew to sleep.
5. These compartments are often located above first class, accessible by a narrow stairway or ladder.
6. The size and design of the compartments vary between airlines.
7. Some compartments have soundproofing, mirrors, cabinets, and entertainment systems.
**Section 3: Loops on Airbus Wings**
8. Some Airbus planes have small yellow loops on the wings.
9. These loops are for emergency escape ropes to prevent slipping on the wings.
10. The ropes are secured to the plane and the loops to facilitate safe evacuation.
**Section 4: Holes in Plane Windows**
11. Plane windows have a small, circular hole (breather hole) in the middle pane.
12. The hole helps equalize pressure between the cabin and the space between the panes.
13. Each window consists of three layers of glass (scratch pane, middle pane, and outer layer).
**Section 5: Hidden Handrail**
14. Most airliners have a hidden handrail along the overhead compartments.
15. The handrail is for crew members to safely move around during turbulence.
**Section 6: Adjustable Armrest**
16. Some aisle seats have an adjustable armrest with a button near the hinge.
17. Pressing the button allows passengers to move the armrest out of the way for more space.