Some were once true and are now obsolete, while others were never true in the first place. Some are like mom’s words: wear clean underwear in case you’re in an accident and go to the hospital. Not about how badly you were hurt, but not be wheeled into the ER in dirty skivies.

Similar rumors insist passenger planes continually recirculate the same used cabin air. You get all the germs other passengers have coughed and sneezed into it. Truth is that all cabin air goes through a filtering system every few minutes, and mixed with outside air before being circulated back into the cabin, and is air cleaner than what you breathe in a store, restaurant and home.

The myth persists because some people do catch colds and flu on trips involving flights, but not from cabin air. It’s from sitting close to sneezing and coughing passengers aboard and in the terminal. Being jammed together with sick people in security, restaurants, rest rooms and other locations is where to catch the latest ailment. Another myth involves when checked luggage is weighed. Is it accurate and you pay the correct fee? Of course, you’re already griping because airlines keep jacking up prices for checking luggage. For accuracy, researchers tested scales at several airports recently .

Surprisingly or not, the average was that some airport scales were as much as 25 percent heavy. On a piece of luggage that actually weighs just 20 pounds and you’re charged for 25 pounds @ $2 a pound, that means you’re paying a rip-off $10.

As with the crooked butcher with his thumb on the scales, the airline could be raking in mucho dinero each day from that one scale and others. What can you do about it? Before you leave home, weigh all bags you’ll be checking. If you know you’re being overcharged, ask the clerk to use another scale. If refused, say you’ll report the overcharge to authorities.

Another rip=off may involve being booked a non-stop, so all you need to do after you board is sit back and fly along uninterrupted to your destination. That will happen most times, but airlines have the right to change the schedule for economy, weather or other reasons.

You’ll still get to your destination eventually, but there may be a previously unannounced stop at an in-between airport for other reasons, such as to pick up more passengers and bring the airline a few extra bucks. You can complain, but it may not get compensation for your lost time.

It’s no myth that frequent flyer points give you free flights. That may have been true a decade or so ago, but like the carrot on the stick, airlines keep raising the requirements to earn free flights. For instance, several years ago it took eight flights to earn a free trip on Southwest.

Now it takes 16 or more. During holidays and other busy flying times, trying to get free flights with frequent flyer points may be useless. The maddening excuse you get is, sorry, but there are only four seats on that flight available for frequent flyers, and they’re already sold.

Another myth is that special seasonal and attractive deal prices quoted by travel agencies, airline ads and in airline online booking sites are always true. However, many allow only 24 to 48 hours for you to book the advertised flight, although it may be scheduled many months away.

For example, if I grab a good price tonight for a flight leaving six months from now, I’ll get a bargain. But, how can the average business person or tourist know what his/her schedule will be six months away? Airline specials are not always myths, but before you book that attractive flight, make sure the timing fits in with your plans. 

There are many more air travel myths that keep passengers confused and worried. However, do your homework on airline practices before booking. Update all info just before you pack, and you should make it through your next trip safe and sound, maybe to visit mythological destinations.