This news story is a bit old but I found it quite interesting and thought it deserved a mention here.
The men and women of World War II faced a lot of obstacles. Not only did they face the enemy firing upon them but the environment in which they flew posed a problem. A team of American physiologists researched the effects flying had on the human body and, in the course of their experiments, used an unlikely subject: a St. Bernard dog.
One doctor made a high-altitude jump to experience the effects the dive would have on the human body and nearly died in the process. However, he was able to use the information from his jump to calculate the exact time a parachute should be opened to limit the impact of the g-forces on the body.
Enter Major, a 145-pound St. Bernard dog. Major was thrown from an airplane 26,000 feet in the air to test parachute straps at a high altitude. He wore a custom oxygen mask and was able to dog paddle all the way to the ground and land safely.
Major's 26,000 foot down dog paddle and the efforts of the doctor before him not only assisted in the war effort but left research that led to modern breathing equipment.
For more information about the research into flying and diving during World War II and Major, please visit the full MSNBC.com Technology and Science Article.