In-flight damage to a supersonic jet I'm doing some research for a book I'm writing, and, as the title implies, I'm looking to understand what happens when a supersonic jet sustains in-flight damage.
Specifically, what happens to the occupants if the cockpit is breached? (I assume that this is why jet pilots wear masks?) Could a jet maintain super sonic speeds (for at least a short time) with such a breach? What would happen to a person in the cockpit without a mask if there was a cockpit breach at those speeds?
Just how weird do things get at super-sonic speeds? Could a conventional airliner ever reach mach one in extreme circumstances?
Many thanks!
 A: Fighter aircraft cockpits are pressurized, otherwise you wouldn't be able to breath even with an oxygen mask. When you breathe out you need the external pressure on your chest to force the air from your lungs. For a short period you can breath with less pressure with low efficiency - which is why you need a richer source of air ie. higher oxygen content, in an airliner emergency mask.
The mask on a fighter pilots helmet is also to provide convenient place to put communications gear and to provide an air supply if the cockpit failed or you had to eject. This does lead to another problem, if you have to eject at high altitude you suffer a rapid loss in pressure - this is equivalent to ascending from underwater too quickly and pilots can get the bends. This is the justification for the airforce having a diving research facility.
Flying at very high altitude aircraft (eg an SR71 or U2) the outside pressure would be too low to allow you to breathe, even with an oxygen mask. This and the high temperature and high speed of the airstream if you had to eject means the crew had to wear pressurized suits.
How long the plane could remain flying would depend on the nature of the damage, there is nothing particular special about supersonic on a small scale - there are still numerous openings, intakes, ports and other holes in supersonic aircraft.
The canopies are pretty strong - bullet proof is generally a user requirement - so they wouldn't shatter on impact. There have been pilots killed by canopy failures or accidental ejections but there are also pilots who have survived the disintegration of an SR71 at mach 3
A: You also ask:

Just how weird do things get at super-sonic speeds? Could a
  conventional airliner ever reach mach one in extreme circumstances?

Things don't especially get "weird" at supersonic speeds. The aerodynamics is different above the speed of sound than below, and that affects the design that goes into the airplane and its engines: how lift is generated, how to handle drag and shock waves, how the engines consume air. But that's all engineering stuff.
As the above implies, an airplane must be designed to go supersonic. The behavior of flight near, at, and above Mach 1 is different than subsonic flight and the craft needs to be engineered with these in mind.  It's not the case that you can just "push" a standard aircraft into exceeding the speed of sound under "extreme circumtances".
The only commercial airliners that were supersonic were the (both now defunct) Concorde and Russian "Charger".
A: 
Specifically, what happens to the occupants if the cockpit is
  breached?

Without supplemental oxygen, the occupants will lose consciousness, or lose the ability to think clearly enough to improve the situation.  This table from the Pilot's Handbook of Aeronautical Knowledge (free FAA publication; search for "hypoxia") might be useful:

Also, if you're not wearing a seatbelt, you can easily be sucked out of a window if the window breaks.  There are several incidences of this occurring.
