Travel is often hectic - rushing to make a plane, keeping an eye on young children, maybe hauling too much baggage.
Distractions can create opportunities for thieves looking for an easy target in a crowded terminal or aeroplane cabin.
Thefts from airline luggage are rare, according to US government figures, but that doesn't ease the sting if it's your holiday that's ruined because of a stolen passport or jewellery.
Experts say most of the thefts that do occur could easily be prevented if travellers followed a few basic rules, starting with the most obvious one.
"Never pack valuables in luggage that you're going to check in," said Bryan Saltzburg of travel website TripAdvisor.com. "Carry it on the plane with you, or ship it insured."
Sometimes airline employees force travellers to check-in a carry-on bag, especially during peak travel periods such as holidays, when planes are crowded and overhead bins fill up quickly.
That's what happened to a New York filmmaker who is suing American Airlines. He says the airline lost his carry-on bag that held irreplaceable footage for documentaries. American asked to have the case dismissed, saying the passenger signed a waiver that limited its liability for lost valuables, but a federal judge in New York is letting the case go ahead.
Saltzburg advises travellers to pack valuables in a smaller bag that fits inside your carry-on suitcase. If a gate agent tells you to check the suitcase, remove the smaller bag and keep it with you - most airlines always allow a personal item such as a small bag or purse that fits under a seat.
You'll also want to get to the gate early and board before the overhead bins fill up.
"People who get their carry-on stolen usually board late," said Kevin Coffey, a police detective and travel-security consultant in Los Angeles. "They're sitting in Row 44, their bag is above Row 19, and when the plane lands, a crook grabs the bag and he's gone."
• Put your bag in the bin across the aisle from your seat, not directly above you, so you can see if someone tries to reach into it during flight.
• Turn the bag and flip it so that zippers are in the back and facing down, making it harder to get into.
• If you go to the bathroom, take your passport, wallet or purse with you.
• Make sure you've got all your belongings before you get off the plane. If something is missing, tell a flight attendant and file reports with the airline and police before you leave the airport.
Last year, two million travellers complained to the US Department of Transportation about mishandled baggage, which includes stolen, lost or delayed bags. That's a big number, but it's only 3.6 incidents for every 1000 passengers, and it's half the rate of complaints lodged just three years earlier.
Celece Seegmiller, owner of The Travel Connection in St George, Utah, suggests buying travel insurance that covers valuables, and don't flash your money or jewellery.
"When you go on a trip," she said, "the first thing to pack is your common sense."