Change: There were only format changes (bold, italics, etc.) in this version. See this version for details. (Word count: 773)

Change: Feeling the pressureYou yawn and chew gum, but your ears still pop on takeoff. Captain Meryl explains what cabin pressure has to do with it.As many as one in three passengers suffers from painful pressure in   View changes from previous version. (Word count: 773)

Change: Airplanes are not sealed tubes, as some may think. Instead, there is a constant flow of fresh air coming into the cabin, supplied by engine   View changes from previous version. (Word count: 776)