Do you smell something funny? Not on an airplane, I hope, because many carriers have rules about odors.

If this sounds crazy, do what I did and read your airline's fine print. You'll find it in the dense legalese of the "contract of carriage" located on most carriers' websites. What it boils down to is the various conditions under which airlines agree to carry you and your belongings, and when they will refuse you.

Some of this is pretty serious stuff; some will strike you as utterly absurd. I've got examples of both and don't miss No. 13 - my nominee for the Captain Obvious award.

1. The Stink Factor

You know how airlines sometimes boot passengers for being "too-fat-to-fly"? They sometimes boot them for being too smelly to fly, too. In fact, most carriers, like American Airline, have a section in the contract of carriage that specifically bans passengers with "an offensive odor." If you believe an airline would never have the guts to enforce this, think again: In 2010, an anonymous flier aboard Air Canada Jazz was asked to leave the plane after efforts to isolate the man from other passengers could not overcome his stench.

2. No Barefoot Flyers

Most airlines including Delta say ditching your shoes on a plane is grounds for ditching you. I know this because once on a long trans-Atlantic flight, my wife decided to get comfortable and slipped off her sandals; a flight attendant quickly and tersely ordered them back on. By the way, JetBlue says "no" to going barefoot, too, unless you're age 5 or younger.

3. Passenger Age Limits

No airline bars passengers for being too old, but you can be too young. Carriers such as United will not accept infants under 7 days old, but US Airways says as long as your baby is 1 day old, that's good enough for them.

4. Pet Odor

 Back to the stink factor: Nearly every airline, including US Airways, says animals transported in cabins must be "odorless" and if you own a dog or cat that has no smell, congratulations are in order. Funny thing, US Airways is one of the few carriers that makes no mention of human odor.

5. Service Animals

Many airlines accept a variety of critters on planes free of charge if they are documented "service animals" and this, of course, includes guide dogs. United Airlines allows you to fly with your service monkey, too, but he'd better be prepared to hunker down under a seat. Virgin America, some may be saddened to learn, draws the line at service snakes, service rodents and service spiders.

6. Pet Oxygen

If there's an emergency during your flight and those oxygen masks drop down, don't look for one to place over Sparky's muzzle if you're flying Southwest; its policy specifically states "no masks for pets." You'll just have to share.

7. Separated from Loved Ones

We've been hearing a lot about families not being able to sit together as more seats are allocated to those willing to pay a fee for them, but at least one airline guarantees you'll sit with someone you love: Virgin America's contract of carriage promises they "will not separate a service animal from its owner." They even let you hold this helpful creature in your arms.

8. Mistake Fares

There have been some infamous "mistake fares" over the years, such as this round-trip steal from Lufthansa back in 2010: Chicago to Frankfurt for an eye-popping US$300+ (the airline forgot to add a surcharge). Sometimes, you can take advantage of these deals, but not with Delta; its contract of carriage states it "reserves the right to correct any erroneously published fare that Delta did not intend to offer for sale." In other words, you might get the deal of the century, but you might not be able to use it.

9. Getting off a Connecting Flight Early

Here's the scenario: You want to fly from L.A. to Las Vegas, but the price is a little steep; then you notice a cheaper deal on a flight from L.A. to Salt Lake that has a stop in Vegas, so you figure you'll just book that ticket and deplane in Sin City. Not so fast. United's fine print says if you engage in this form of "cheating" they can cancel your flight home, cancel other reservations, even cancel your elite status in the miles program.

If by chance you do try this anyway and are foolish enough to have checked a bag, that bag won't get off early with you -- it'll go on to your flight's final destination -- so be prepared to buy some clothes.

10. Free Lodging

Though increasingly rare, under certain circumstances, some airlines may put you up for the night if a flight is canceled. However, United won't give you a free hotel room if you're stuck at your home airport, which is fair enough. Not so fair: The airline won't put you up if you're stuck at an airport near your home. Example: You fly out of Southern California's Ontario, your home airport, then your flight gets diverted to or otherwise stuck at LAX. United says you must make the 50+ mile drive home, then do it again when the flight resumes. If you know anything about L.A. freeways you know you've just been sentenced to traffic hell.

11. Bad Habits

You know there's no smoking aboard any U.S. airliner, but maybe you don't know that most carriers also ban electronic cigarettes. United does; it also bars passengers from chewing betel nuts.

12. Baggage Losses

Most airline "fine print" mentions several items they are not responsible for when bags are lost such as jewelry, cash and electronics. Other items not covered include eyeglasses, medications and even non-prescription sunglasses. Frontier also won"t cover lost antlers and better hope your Bible doesn't go missing on United since they don't cover religious items.

13. Watch Your Outfit

You might be surprised to learn that many airlines care what you wear. American says it can throw you off the plane if you "are clothed in a manner that would cause discomfort or offense to other passengers" and just a few weeks ago a woman sporting a T-shirt featuring the F-word did get the boot. Virgin America takes it a step further. It reminds passengers that refuse to transport "any guest who is not wearing both top and bottom apparel." Now there's an airline that believes in spelling things out for you.