You’ve surely heard this one a number of times before, that the emergency exit doors on commercial flights can be opened by a dastardly, careless (or drunk) passenger on board. You’d be correct to worry if this were feasible, as the immediate change in air pressure would be fatal at heights of tens of thousands of feet; however, the door is kept closed by more than a flimsy mechanism which can be overridden at any time by a stray hand. Emergency doors have been intentionally engineered to open only when the air pressure inside and outside of the aircraft is at an equilibrium, a passenger would need seriously superhuman strength to budge it.
This myth has been tried and tested and there is nothing scientific to support the idea that you get drunk faster when you're at a cruising altitude. But because planes are not pressurized to sea level (it's the equivalent of breathing at about 8,000 feet up), there's less oxygen in the air, which can make you feel drunk.
You can get stuck, but only if your body forms a perfect seal on the vacuum toilet. This is difficult to do. Yes, if the toilet bowl and seat had an airtight seal, this might have nasty consequences for toilet users who flush when seated. But the toilets and the vacuum system are designed in such a way that you cannot be sucked into the toilet.
Many people believe the air on a plane is stagnant and full of germs. In reality, the air in an aeroplane is heavily filtered and carries fewer germs than the air in most crowded spaces. Passengers on board an aircraft breathe in a mixture of fresh air and recirculated air. The supply of air comes from the compressor sections of the engines, it is cooled and then run through filters and then re-mixed with a fresh supply from the engine. Underfloor filters are used to treat the cabin air are described by Boeing as being of 'hospital quality' and capturing between 94 and 99.9 percent of airborne microbes.
Think of this as similar to wearing a seatbelt in a car. While it's not crazy to think that your seatbelt can hinder a hasty escape from a crashed plane, it does far more good than harm. In a situation like that, you would potentially be thrown out of your seat, and could hit another passenger or a bulkhead. So it's better to be in your seat and have to deal with unbuckling, than to find yourself flying through the air.
If the cabin loses pressure (which can easily happen without leading to a crash), everyone on board is left breathing the air at 30,000 feet, which is oxygen-poor (the summit of Mt Everest is 29,029 feet high).Until the pilots can bring the plane down to about 10,000 feet, where the air is safely oxygen-rich, those masks keep everyone breathing normally. That's fairly important. So, oxygen masks really do help you breathe at high-altitudes, where rich oxygen is scarce.