Stories about human poop falling out of clear skies have become a staple of weird news. Sometimes it crashes through a roof, or it might break the windshield of a car. Most recently, the Cambray family of Pennsylvania was celebrating their daughter's sweet 16 birthday when, so they said, poop began raining down. The birthday girl's sister told a reporter, "It was brown. It was everywhere." 

Falling human poop is an unusual byproduct of the Age of Flight, coming as it does from planes that pass overhead.

In the interest of shedding some light on this dark matter, here are 12 facts you might not know about the history of this phenomenon.

1) Lindbergh was the first on record to dump waste from a plane

The earliest recorded example of human waste (not poop, specifically) falling from a plane dates back to May 1927 when Charles Lindbergh flew nonstop from New York to Le Bourget Field in Paris. During a reception afterwards with King George V of England, the King, overcome by curiosity, asked Lindbergh how he had gone to the bathroom during the flight. Lindberg explained that he had peed into an aluminum container which he had dropped somewhere over France. He added, "I was not going to be caught with the thing on me at Le Bourget."

2) Early aviators just flung it overboard

During the early years of aviation, waste was generally thrown overboard in containers, or the onboard toilet was simply a hole in the floor. The assumption was that the waste would vaporize before it hit the ground. It wasn't until the 1930s that airlines realized the stuff wasn't vaporizing in mid-air and  began to store it in onboard containers, which were pumped out after landing.

But since then, commercial airlines have never purposefully dumped waste mid-flight. In fact, it's impossible for a pilot to intentionally dump toilet waste. The drain plugs can only be opened by crews on the ground.

3)  Longer flights changed the character of falling poop

The introduction of transcontinental routes by commercial airlines in the mid-20th Century meant that planes flew at higher, chillier altitudes. So when the onboard waste containers leaked, which they inevitably did because of wear-and-tear on the drain plugs, dribbles of waste froze on the outside of the planes, eventually falling off in chunks that were sometimes big enough to smash through people's roofs. So longer flights transformed falling waste from something that was only kind of gross, into something that was actually very dangerous.

4) Falling poop began making headlines in 1957

In September 1957, a 100-pound block of ice fell on a clear day in Chester, Pennsylvania, crashing through the slate roof of a vacant building. By the end of that year, more chunks had fallen in Philadelphia, Bernville, Shamokin, and Camp Hill. Tests by the U.S. Public Health Service found that some of this ice contained "soap and towel fibers," which meant that it couldn't have been produced by a meteorological phenomenon. It must have come from planes.

5) By the 1970s, falling poop had become known as "Blue Ice"

The soap referred to in the Public Health Service report was probably the blue/green disinfecting liquid used to flush and sanitize onboard toilets. As the years passed, and ice chunks continued to fall, this colored disinfectant became a distinguishing feature of frozen chunks of airliner poop, earning it the nickname "Blue Ice."

6) A series of highly publicized cases in the 1970s made falling poop a subject of national debate.

One of the first of these cases occurred in May 1973, when a green "waste bomb" smashed through the roof of Esther Kochanowicz in upstate New York. It struck her favorite chair, then burst into pieces in her living room. Another case occurred in October 1976, when a 12-inch ball of blue ice shattered against the Chicago house of Walter Grzybowski, as he was playing with his dog in the backyard. Grzybowski reported that his dog promptly started licking the ice. 

7) No one has ever been killed by falling poop, but one lady came close

On October 10, 1974, 77-year-old Erma Schun was sitting in her Lansing, Michigan apartment when a block of ice crashed through her roof, missing her by only 6 feet. She said, "It was like an atom bomb." The event made the Evening News with Walter Cronkite. Two months later Schun died from a heart attack, which the stress of the incident may have contributed to. 

8) The 1970's poop panic prompted the FAA to consider various solutions

Some of the solutions the agency considered were external heaters and Teflon-coated paneling, but it eventually decided that these changes were impractical and ruled that increased maintenance could safely reduce the hazard.

9) In the summer of 1991, a series of Blue Ice falls plagued Long Island

The early 1990s was another period of widespread poop panic, after numerous ice falls were reported in Long Island. One chunk broke through the windshield of a car. Another crashed through the wood deck of a house in Lendenhurst. One married couple, sitting on their patio, was splattered by fragments of frozen poop that hit the side of their garage and shattered.

10) Thanks to vacuum toilets, falling poop is no necessarily longer blue

In 1982, vacuum toilets were first installed on planes, and since then have become widely adopted. These eliminate the use of disinfectant liquid. So if anything does leak, freeze, and fall, it isn't blue. However, vacuum toilets have evidently not eliminated the problem of falling poop, because poop falls continue to be reported.

11) The FAA advises people not to store fallen poop in their freezer

When poop hits a house, the first thing the homeowners typically do is put some of the poop in the freezer, thinking this will help investigators to identify its source. However, the FAA cautions that this is not a good idea. FAA spokesman Fred O'Donnell, in a 1990 interview, noted, "It's just not the kind of thing you want in the refrigerator."

12) Most falling poop isn't from planes

Plenty of poop falls from the sky, and the vast majority of it doesn't come from planes. Birds are the culprit. The FAA receives numerous complaints about falling poop every year and says, "when we investigate the phone calls regarding the brown droplets, virtually all of them involve bird waste." It also notes that bird poop can be blue or green depending on what the birds have been eating.