Effects as a function of altitude. The human body can perform best at sea level, where the atmospheric pressure is 101,325 Pa or 1013.25 millibars (or 1 atm, by definition). The concentration of oxygen (O2) in sea-level air is 20.9%, so the partial pressure of O2 (pO2) is 21.136 kPa.
On Tuesday, the New York-based carrier rolled out a new three-tier structure for fares, giving the cheapest fares to passengers without checked bags. The airline's new fare types are labeled Blue, Blue Plus and Blue Flex, according to notices posted on JetBlue.com. Price differences between the tiers will vary, but Blue fares generally will be $15 cheaper than Blue Plus, and Blue Flex will be about $85 higher than that, according to JetBlue.
If flying on a Blue fare, the cost to check the first bag ranges between $20 and $25 depending on when purchased, and a second bag costs $35. Passengers opting for Blue Plus fare will get one checked bag included and pay $35 for the second bag. Those on Blue Flex fares are allowed two free checked bags. All additional checked bags will cost $100 each, JetBlue said.