U.S. airlines are stepping up measures to guard against the spread of coronavirus through person-to-person contamination on airplanes, from eliminating wine and water refills to keeping passengers from touching serving trays and food baskets.

Rather than bringing wine or water bottles into the aisles for refills, flight attendants on United Airlines will now provide a new cup or glass.

Facing a sharp drop in travel demand due to rising coronavirus outbreaks across the world, airlines are offering travelers free rebooking options while trying to calm jitters about cabin cleanliness and air-circulation systems.

In a letter to customers on Saturday, United Airlines Holdings Inc Chief Executive Oscar Munoz said it is "important that we give you as much information as possible about the procedures we follow to clean our aircraft and maintain a sanitary environment once we're in the air."

In addition to extra cabin-cleaning measures including washing ceilings and scrubbing overhead bins, United said its flight attendants may wear gloves during all food and beverage service and pickup.

Delta Air Lines and American Airlines Group Inc have also introduced extra cabin protections, including eliminating self-serve snack and fruit baskets, and all of the carriers are working with airports to regularly disinfect common surfaces like kiosks and ticket counters.

Airlines and flight attendant unions have also been retaining infectious disease and aviation medicine experts for town hall meetings with crew members to explain best practices like frequent hand-washing to protect against contracting the virus.

"Unfortunately, there is risk involved in this line of work, and exposure to passengers carrying disease is one of those risks," Dr Kris Belland, a medical adviser for the union representing American Airlines' flight attendants, said in a letter to crew.

There are now 102,000 coronavirus cases and more than 3,480 deaths across the world, according to a Reuters tally of government announcements. Most cases and deaths have been in China but numbers are mounting outside its borders, with around 90 other countries reporting infections.

Airline stocks have plummeted as worries about the impact of the coronavirus on the economy have taken hold. On Wall Street, the broad S&P 500 index has dropped more than 12% from its Feb. 19 high, with the NYSE ARCA airline index down nearly 31% over the same time frame.