U.S. Military fighters trailing unresp. aircraft in Atlantic... UPDATE: Plane crashed near Jamaica

Many un pressurised single engine aircraft are capable of flight above 10k... It's more efficient in many cases.
Even my lowly piper Cherokee is capable of 14k. Short periods above 10k are ok without oxygen, above 14k you are supposed to have oxy on at all times. Pressurisation is not required, just something to breathe...

To cruise at height for efficiency you just use a portable oxygen system. Cheap and effective, just a cannula under the nose or basic mask...

As for masks dropping upon loss of cabin pressure... The aircraft here is no airliner. The crew have masks available, passengers generally don't. In the event of an issue the idea is the pilot dons their mask and descends to below 10k for the passenger comfort.

....hypoxia, low oxygen ...No, brain damage is NOT an issue at 25k... Unconsciousness, but just fine upon coming around(once the shocking headache wears off) ANOXIA...the absence of oxygen, THAT will cause brain damage or death... Much higher altitudes for that issue.

Outflow valve... Yes possible, but also possible is a pressurisation pack failure... If pressure is not coming in a working valve on the way out won't help... That said, valve more likely as pack failure would be less subtle.

a reply to: _BoneZ_

Looking for the archives on LiveATC.

I like LiveATC, you can hear all kinds of traffic if you know what to listen for.

a reply to: Wingspan

Pack failure is also less common than valve failure. At least in my experience.

I wonder why all of a sudden, there are so many planes going "unresponsive" and missing. There are what, like, eleven so far, over seas. Then, there is all this hype on MSM and even the web, bringing up the n*ne eleven anniversary and fears of t*rrorism in September. Also, all kinds of reports of missing radioactive material...and one should still wonder about that BAFB debacle and Minot and the miscounted nukes...Wasn't Payne Stewart in those skies right around when all that went down. Did he witness something. Just speculating so no shorts need to get in a bunch...that is why a site like this is interesting and entertaining and more.

a reply to: shrevegal

Its because your are made aware of it. Like Zaphod said, two in one week is nothing compared to the million flights done per week.
(even 20 would be real low, although sad)

a reply to: shrevegal

I get alerts every day for planes that are comms out, usually several a day. It's a normal occurrence, but 99.9% of the time it's a matter of a pilot missing a frequency change.

archive-server.liveatc.net...

Starting about 4:10 you can hear them talking to N900KN. Eventually he starts to sound like he's slurring his words just a little, and he twice acknowledges instructions to descend to 20,000 feet from 25,000 but he never descends and eventually stops responding. The controllers eventually have other aircraft attempt to contact him as well as other controllers.