Don’t pilots in fighter jets or other unpressurized planes need to keep their masks on at altitude?
In the movies, they generally leave it off, only putting it on for dogfights. It doesn’t seem like they would be function very long in the thin air, so I’m assuming this is a Hollywood fabrication. You want to be able to see the actor’s face, right?
Fighter jets are pressurized. I am pretty sure the masks are for backup, considering the likelyhood of damage to the pressure vessel which could render the pilot unconscious.
IANA pilot, but virtualy all modern jets are pressurized, including fighters.
Fighter jets are pressurized, just not AS pressurized as something more familiar, like a commercial jetliner.
For example, a commercial jet cruising at 35,000 ft would have (depending on the type) a cabin altitude of around 6-7,000 ft. The pressurization system holds the differential at 7.5-8.5 psid, once again with variations among airframes. This allows the aircraft to cruise at altitude while keeping the cabin livable, and specifically below 10,000 ft.
Fighters typically use a lower psid, so that at 35,000 ft the cabin altitude might be 13,000 ft or so. The goal of a pressurized fighter cockpit is to avoid most of the unpleasantness associated with exposure to high pressure altitudes - internal gas expansion, the bends, etc. A lower psid can achieve this and also allow the designers to have some “leakage” during high-performance maneuvers without any ill effects.
As for the wearing of the mask, most of what you see in the movies is exactly what you guessed: Hollywood nonsense so you can recognize who is flying. However, guys do sometimes fly without their masks. Anytime the cabin altitude is below 10,000 ft you can drop your mask with no worries - and sometimes you just have to get at that itch! If you’re cruising at anything under 29,000 feet or so, you could fly all day with your mask off. And “off” doesn’t always mean “off” like in the movies. Just unclicking those bayonets a couple of notches can make life much more bearable, even though you don’t have a good “seal”.
Most training sorties in fighters last under two hours, and usually the mask never comes off the entire time. On longer missions (like what they’re doing over Iraq right now), most people will drop the mask for a while, especially on a 6-hour mission.
The mask provides oxygen constantly, and is critical in case something goes wrong. It can be a problem with the pressurization system, or in extreme cases if the airplane is damaged at altitude and depressurizes. It also provides protection for the face in case of a birdstrike, debris entering the cockpit and during ejection.
pilot141 - you sound like you were/are actually a fighter pilot? I bet there would be a lot of demand for an “ask the fighter pilot” thread. I know we’ve had an overload of those, but I think it’s one job a lot of us know very little about, except for the “information” we get from Top Gun and military flight sims 
When I was flying the T28* (later used in Viet Nam) in flight school, we only used a mask once. That was the flight just before we hit the carrier. It was just a goof off flight and they told us to go to 10,000 feet and practice our pattern. 
Anyway, are you talking about old movies or Tom Cruise vintage? If they are flying low to avoid radar there would be no use in wearing the mask.
[sup]* one of the 300 T-28Cs built by North American Aviation, was accepted by the Navy on May 16, 1957. The plane served in the Gulf of Mexico on two carriers, the Antietam and the Lexington, which sailed training cruises between Pensacola, Fla., and Corpus Christi, Tex., until the late 1970s[/sup]
DarrenS , I flew jets for the Air Force for 11 years active duty but only one year was in something like a fighter - the T-38 “white rocket”:http://www.af.mil/photos/images/trainers_t38_0003.jpg
This gave me enough experience with a mask to know what works and what doesn’t! Talking with buddies of mine flying fighters over the years is how I came up with the info about long missions.
Probably not much demand for the “ask the cargo then trainer then airline pilot” thread! 
Let’s try that link again:
For what it’s worth, there was a case a while back here in Australia of a pilot who crashed his F/A-18.
This particular pilot was in the habit of not wearing his mask, a la Tom Cruise/Top Gun.
The last time his wingman saw him alive he was slumped at the controls of the aircraft with his mask off. The plane later slammed into the ground.
I don’t know much else about the circumstances of this particular crash (ie altitude etc)… but worth thinking about I guess.
Max.
Maxxxie , this has happened in the US as well. The specific case that I know of is an F-4 pilot who took off with his mask hanging. The airplane never pressurized and the pilot lost consciousness, never regained it and crashed. The Air Force has the tape of his wingman yelling at him trying to wake him up to no avail. The Air Force uses this tape during altitude chamber training - you get to listen to this right before you drop your mask at high altitude and go hypoxic.
Actually, this happens somewhat routinely in the Navy, and my guess would be in the AF as well. If you’re involved in aviation, you get “chamber rides” which is where they throw you in a low-pressure chamber and take you to about 25k feet. The goal is to get you hypoxic so that if you’re ever in an aircraft, you’ll recognize the effects and take the appropriate action (either getting your O2 mask on or checking the settings on the O2 system).
What happens sometimes is that, either through malfunction or operator error (usually a rushed preflight in which a step is missed), aviators find themselves at altitude getting hypoxic. Usually they recognize the effects (thanks to the chamber rides) and fix the problem before they get too hypoxic to care. You don’t hear about these because no one really cares outside of the aviation world and also because many pilots, no doubt, don’t report their mistake.
I went throught the chamber at Edwards AFB. Quite fun! I wish I could do it again. (I read that it had been closed a year or so ago.)
IIRC, there are different rules for the Navy and the air force. IIRC the Navy requires O[sub]2[/sub] above 10,000 feet, while the air force requires it from take-off. Could be the other way around, but I think that’s right. And of course, the rules may have changed since I got my “orange card”.
For the Navy, O2 is required for cabin altitudes above ten thousand.
Actually, Johnny, I just did my 4-year chamber ride last Monday, which is my second to date. The first one (1995) was kind of fun, but this last one wasn’t. I got light-headed, which is the same way it affected me the first time, but this time I didn’t feel like toughing it out. I can still function for a while like that, but I realized that I really didn’t like doing things with my head feeling like that. In other words, it was no longer fun. So after ten or so seconds of feeling light headed, I put my mask on and felt normal.
As a slight hijack, an EP-3 crew did experience a slow depressurization at altitude many years ago. The pilots figured out what was happening and donned their masks. But for the crew in the back, it was different. We don’t have masks. Instead we have aviox cannisters, which require pulling off the cap, pulling some sort of tab, rotating a ring, then pulling out a pin (I’m sure this isn’t the exact way… I’m going off hazy three year memory)… the procedure isn’t user-friendly. Only one or two folks in the back end of the aircraft managed to get their bottle working. The rest either didn’t try our couldn’t make the thing work. Fortunately, one step of the emergency procedure for depressurization is to descend below ten thousand, so everyone was fine, minus a bunch of bad headaches.
