Attention all passengers on Air Optimism (that is, those who didn't grab a parachute and bail out following last week's PowerBook no-show): expectations for Mac OS X 10.3, a.k.a. Panther, are beginning their descent. Please stow your unbridled enthusiasm in the overhead bin or underneath the seat in front of you and return your tray tables and seat backs to their full upright and locked positions. Now, don't worry, there's no need to assume crash positions just yet; there's no evidence that Panther's not everything and a snack-size bag of Baked Lays, or anything like that. Panther will rock. Panther will rock so hard your ears will bleed. (Okay, ewww.) We're just giving you a little warning to scale back your possible expectations as to a ship date.

Now, you probably recall that everything about Uncle Steve's Panther demo during the WWDC keynote was met with audience approval ranging in intensity from "appreciative nod and murmur of assent" (fast PDF rendering in Preview) to "uncontrollable screaming, tears of joy, tossing underwear on stage" (Exposé). Well, almost everything. The revelation that Panther will ship "by the end of the year" prompted stony silence except for the sound of crickets chirping, tumbleweeds tumbling, and the hopes and dreams of many a Mac fan withering away just a teensy bit. Having to wait potentially until New Year's Eve to enjoy Panther's smorgasbord of nifty new features seemed, if anything, cruel and unusual punishment for some unknown sin, and most of us wondered whose dog we had run over in a previous life to come to this sorry end.

Of course, most of us then came to our senses, realized that there are far worse fates than having to wait until year's end for a Mac OS X upgrade (heck, there are hundreds involving Steve Ballmer jogging naked on a treadmill alone), and moved on. Suicides attributed to the end-of-year ship date were few and far between.

But then, hope! Early July rumors sprang forth that Panther might surface "much more quickly" than December 31st, and separate rumors a month later concurred: Panther development was proceeding so quickly, the whispers said, that it might full well still ship by its alleged originally planned release date of mid-September. And since Apple Expo throws open its doors on September 16th, that date emerged as the de facto official target circled in red on everyone's Society of Mac Rumor Optimists 2003 calendar. (Incidentally, if you don't own one, the picture for September is captioned "Spy photo: Steve Jobs test-drives Mac OS X on a stock x86-based Dell laptop after approving the Apple-Disney merger," but upon close inspection appears to be a blurry snapshot of a Piggly Wiggly taken without a lens as the photographer drove past at 80 MPH.)

Now, though, it's getting harder to see September 16th as the light at the end of the tunnel. Apple reportedly seeded build 7B44 of Panther to developers late last week, and according to AppleInsider, the latest build completely overhauled FileVault (which provides the automatic encryption of files in a user's home directory), rendering previously-encrypted data incompatible. Apple has also switched from tcsh to bash as the default UNIX shell in Terminal, allegedly to "conform to today's emerging linux standards" (although we bet it was mostly because nobody could agree on how to pronounce "tcsh"). Considering that September 16th is just three weeks away, if Apple really intended to ship by the Paris show, we doubt it'd be making such major changes this late in the game. In fact, Panther would probably have to be at or very near to Golden Master status in order to hit a September 16th ship date at this point. There's still a chance, but not much of one.

So, Mac OS Rumors's more conservative Panther ship date estimate of mid-October is seeming a lot more likely right now, but hey, that still beats late December. And the good news is, according to AppleInsider, "one source notes that [Panther] is increasingly reaching the 'snappiness' and speed of Mac OS 9 on a PowerMac G4," so it really is going to be worth the wait-- even if it doesn't ship until March. But, uh, don't tell that to anyone at Apple, okay?