The key is to demonstrate both travel and social etiquette. If a passenger is vomiting, ask a flight attendant if there’s another seat available, said Angelina Aucello, a contributor at popular air travel blog BoardingArea. Yes, flights are often booked to capacity, but if there is an extra seat, moving can help salvage your own flight experience while still being sympathetic to your sickened seatmate.

“Be discreet and polite to the passenger,” Aucello explained. “Tell them you want to give them extra room. You don’t want the person feeling like they’re a burden, [because] obviously they don’t want to be sick. This way you can all be comfortable.”

Outside of nausea, you may want to distance yourself from a passenger who is flying when sick with a cold or flu. If you can’t physically move but are concerned you will get sick yourself, you can kindly say something like, “‘I’m struggling to stay healthy, can I give you a tissue to cough into?'” says Diane Gottsman, author of Modern Etiquette for a Better Life and founder of The Protocol School of Texas. Asking in a compassionate voice will help their comfort level.

If it is a cough, consider also offering them a mint or other medicine you may have, Gottsman added.

That said, you’re still on an airplane—air is circulated no matter what, whether it’s two feet away or three rows back, said Aucello. If you’re traveling abroad, there’s an even greater chance travelers will be exposed to new bacteria and viruses that make the trip home. In which case, Aucello and Gottsman stress passengers be proactive.

“My responsibility as a traveler is to keep myself healthy,” said Aucello, who added she likes to take Zinc supplements and use emergency packets of vitamins to keep her immune system at peak levels. There’s also evidence that compounds found in green tea can help the body fight against infection.

For Gottsman, it’s important to pack an alcohol-based sanitizer in case in the same way “you’d pack a snack in case you get hungry.” The sanitzer can cleanse your hands, your arm rest, and tray table. (It can even be useful for a sneezing seatmate.) If you have a particularly weak immune system, packing a surgical mask can offer better protection from germs.

The bottom line: Sick passengers are as much a part of air travel as lengthy security lines and shaky turbulence. At the end of the day, Aucello and Gottsman said, you just need to keep things in perspective.

“You’re in a public space, people will be sick,” Aucello said. “You don’t know what you’re signing up for when you fly.”

Lastly, remember to maintain a level-headed sense of understanding, Gottsman said. After all, she said, do you really expect or even want the pilot to reroute the plane and make an emergency landing?

“We don’t want to publicly make a big scene, because then the focus turns on us,” she said. “Put yourself in someone else’s shoes … you may not have any idea how sick they really are.”