No you dont

Flight suits do nothing to counteract g-forces. Flight suits are worn because they are made of nomex, a fire retardant material which protects you from cockpit fires. A g-suit protectus you from g-forces, but that only covers the lower torso and the legs. It constricts the lower torso and legs to force blood back up to the brain so you dont black out from g's. But g's up to 7.5 are regularly pulled by the Blue Angels, who dont wear g-suits at all. So you could fly in a t-shirt...or naked for that matter.

On the above comment

As the previous comment points out, yes it is possible to fly without g-suits, even naked. HOWEVER, the US armed forces do require pilots of manoeuverable aircraft to wear these suits for safety... yes, they don't want a fighter pilot blacking out. The Blue Angels can only pull so many g's unprotected because they train their bodies night and day to sustain 7 g's (and to fly aerobatics at the same time). A person of average strength or less (and who does not know how to contract their leg and torso muscles to keep the blood from falling) will pass out at about 4 to 5 g's (sustained over a few seconds, of course... we all have felt 4 g's at the tightest points in roller coaster turns). A trained fighter pilot in good shape will stay conscious at 6 or 7 g's. It's not easy even for the Blue Angels.. watch videos of them in the cockpit during tight turns and loops - they will be grunting and groaning and screaming and distorting their faces... it's quite funny, actually, looks like a terribly BAD number two...

Add on to the last comment...

The cockpits in the Blue Angel jets are modified so it'll be easier. Check out cockpit footage of there legs. The legs are higher then in normal jets.

On all above comments.

The reason they don't wear suits is because the millitary don't have the resouces. They just need planes in the air to do basic take off, fly, and shoot manouvers. The inexperienced pilots are not performing any moves that cause high G-forces, therefore, no 'g-suit' or anything is needed.

Protocols vs. Time, among other things

What if you don't have time to change into your flight suit? Besides, aren't g-forces tolerable unless you really punch it? If you're just cruisin' along, not goin' real fast, aren't the g-forces okay?

Guys!

Come on! We already saw that they were desperate for pilots, which is why they aksed anyone with any flying experience to come forward. Randy Quaid's character was wearing his normal clothes and it's highly unlikely that they had the proper uniforms for everyone else. This should be refuted.