Globe-Trotting, Step by Step

Q. Can you give us information on round-the-world flights, possibly including China, Cambodia and Italy?

Frank Crawford, Chevy Chase

A. A round-the-world ticket is actually a batch of one-way tickets that allow you to make multiple stops in different countries. Tickets are best purchased through a consolidator specialist, such as BootsnAll.com (888-379-9411, http://www.bootsnall.com/) or Air Brokers International (800-883-3273, http://www.airbrokers.com/), or through an airline participating in a code-sharing alliance, such as OneWorld ( http://www.oneworld.com/) or Star Alliance ( http://www.staralliance.com/).

Alliances often have more restrictions. For example, you must fly around the world in one direction only (either completely eastbound or westbound). You're also limited to either a predetermined number of miles you can travel or the number of continents you can visit; alliances differ on their policies. However, the tickets are more open-ended than those offered by consolidators, meaning that you don't necessarily need a precise itinerary. (On OneWorld, for instance, you must book your first international flight but can leave all your subsequent flights open-dated. You can then schedule your trip at no extra charge as you go.)

Consolidators request a more specific itinerary and may charge extra when you need to change a ticket along the way. However, you have more flexibility to zigzag around the globe as you please and are not limited to a specific set of airlines, as you would be by purchasing a ticket through an alliance. A consolidator's ticket runs around $2,000 to $2,500. Starting prices through OneWorld are $3,900 to visit three continents and $5,300 for six.

BootsnAll.com executive Sean Keener suggests that you rank your desired destinations, then get estimates from consolidators and alliances.

"If the quote fits your budget, bingo! If not, start scraping away stops or adjusting locations," Keener says. One way to keep costs down is to use major airports, he says.

Check the consolidators' and alliances' Web sites for more tips.

Can my elderly father bring oxygen through airport security? Will security let a family member without a ticket accompany him to the gate?

Petrina Murphy, Oakton

Supplemental oxygen used for medical reasons is permitted through security checkpoints, according Transportation Security Administration regulations. Other respiratory-related devices, including nebulizers and respirators, also are allowed.

Upon arriving at security, you'll be asked to disconnect the equipment so that it can be X-rayed; if you can't disconnect it for health reasons, ask a security officer for an alternative inspection, the TSA says on its Web site ( http://www.tsa.gov/).