Q. What will happen to my frequent-flier miles if Delta and Northwest decide to go ahead with a merger?

A. Don't worry about losing your hard-earned miles. They won't go anywhere, although finding an open seat to your favorite destination will probably be tougher after a merger than it already is.

When American Airlines acquired TWA in 2001, it also absorbed the carrier's mileage program. Members of TWA's Aviators program were allowed to transfer their miles into American's AAdvantage account at no charge.

You can expect the same thing to happen if Delta and Northwest merge. Tim Winship, editor of the Web site Frequentflier.com, says the programs are so similar that it's unlikely you'll notice much difference in them.

But here's the catch: Combining the memberships of two programs doesn't mean there will be more available seats to fliers.

Q. Do I need a visa for a three-week visit to Ho Chi Minh City? What about vaccinations? - J.E., San Jose

A. You'll need a visa and vaccinations.

Call the Vietnamese Consulate General in San Francisco (415-922-1577) for visa information, but be forewarned: We've had trouble in the past reaching someone in that office, so getting them to process your application may take time.

You can download a visa application at www.vietnamembassy.us or use a visa service such as Casto Travel in Santa Clara (www.casto.com) or Peninsula Visa in San Jose (www.peninsulavisa.com). Expect to pay $65 for the visa; service fees are additional. Processing time is about four days.

Talk to your doctor about vaccinations, but you'll likely need shots for Hepatitis A and B, polio and tetanus. A typhoid immunization can be taken in pill form - three pills over five or six days, we were told by a colleague who has visited Vietnam.

According to the Centers for Disease Control (www.cdc.gov), you should get your shots four to six weeks before traveling to ensure they take effect.