Flies do not explode at high altitude but they may not be able to breath for the same reason a human can’t breath above 18k without either pressurization or supplemental oxygen. Bottles and cans are affected because their skins trap the pressure, negative or positive. Remember, it’s not less oxygen at altitude, it’s less pressure to force he fewer oxygen molecules per volume of air into your lungs.
So today here I was humming along at FL090, some 7000 ft AGL, outside air temp 10 C.
Suddenly two flies (not even all that big) find their end on my windscreen. I have never seen such a thing, have you?
Funny advice on maybe learning how to set QNH correctly or to check blood O2 saturation are not appreciated 
One splash was red, so the bugger even made it up with full payload. Maybe he had stung someone who’s on steroids or so?
Now that we are talking trivia.. Someone wanted to give me some very nice vintage Champagne bottles for me to take on board.
I did not take them because I didn’t want to risk a Formula 1 win celebration event on board, especially because older bottles may suffer from cork degradation. Am I to careful? In hindsight I could have put them in the separate bag compartment, maybe in a large plastic bag or so..
Well, we can always organise a fly-in at Colmar, I’ll donate them.
aart wrote:
I have never seen such a thing, have you?
The other day over Normandy or Brittany at FL080 there was a big one that splashed my windscreen.
So what makes them go up there? In my case it could not have been an updraft. I can see the use for migratory birds, and there must be some reason for large birds of prey to go up high, but insects?
aart wrote:
Now that we are talking trivia.. Someone wanted to give me some very nice vintage Champagne bottles for me to take on board.
I did not take them because I didn’t want to risk a Formula 1 win celebration event on board, especially because older bottles may suffer from cork degradation. Am I to careful? In hindsight I could have put them in the separate bag compartment, maybe in a large plastic bag or so..
There is very little air in the bottle, why would it explode?The dissolved gas will only be released if the air pressure in the bottle drops.
I am hardly a wine thermodynamics expert but I think the pressure in a wine bottle will be the vapour pressure of the liquid, for the given temperature.
Same in say a can of Coke or whatever fizzy drink.
Same in a bottle of pure water actually, except the vapour pressure will be very low.
The amount of air in the bottle, or it’s composition, should not matter.
What matters is the temperature, as anyone who carelessly cracked open a can of Coke in a car on a hot day will testify 
Whether the bottle might explode in a reduced ambient pressure is a matter of how much margin there is in the strength. IMHO, if it was that close, we would have loads of wine bottles exploding in air freight, where the hold pressure is the normal airliner cabin of about 8000ft. So 8000ft must be perfectly OK.
I very much doubt that even 18000ft (500mb i.e. a 50% drop in pressure) will be a problem and I have often carried all kinds of stuff, up to FL210, back from say Greece or Spain. But then I carry that stuff way back in the luggage space, partly to get better MPG and partly because it is near-freezing back there.
OK Peter, I’ll take them next time. Should you be wrong and the cork comes off, the only sensible thing i can think of doing is to take a sip on your health.
JasonC wrote:
There is very little air in the bottle, why would it explode?
I think he was worried that the pressure differential would push the cork out. Did those bottles have muselets (a muselet is a cork with a disc secured by agraffe)?
aart wrote:
Now that we are talking trivia.. Someone wanted to give me some very nice vintage Champagne bottles for me to take on board.
I did not take them because I didn’t want to risk a Formula 1 win celebration event on board, especially because older bottles may suffer from cork degradation.
First off, I’m sure thousands of champagne bottles are transported in the cabin of airliners every day. As the cabin of almost all commercial a/c ‘flies’ at around 8500 ft, definitely no issue there. Can personally attest to champagne surviving around 12k ft unharmed.
What makes thing explode is the pressure difference, if that exceeds te strengh of whatever is holding it in, it gets messy.
For a conpletely rigid container, such as a bottle, it makes no difference what it is filled with, gas or liquid. The internal pressure is constant, the pressure difference increases as outside pressure decreases. A champagne bottle has about 5 bar internal pressure, and actually more than that before the yeast is removed and the dosage is added, so going to FL180 would only increase this to 5.5 bar, which the bottle can take.
For a container that can expand, this is completely different – for example a fuel jerry-can. As outside pressure decreases, the container expands slightly, which lowers the internal pressure. This expansion continues until the additional pressure from the deformation and the outside pressure taken together match the internal pressure. If it is mostly filled with a liquid, which is nearly incompressible, it expands very little. If it is filled mostly with air, it will expand a lot more, and the pressure difference will be higher. Hence flexible containers should be filled to the brim when possible.
