Just what's in that airline snack?

— -- Airline food is getting healthier, but there's plenty of room for improvement.

So concludes Charles Stuart Platkin, a nutritional expert who has analyzed nine U.S. airlines' snacks and meals for coach passengers. United Airlines, the USA's No. 2 carrier, serves the most nutritious food and was given Platkin's highest "health score," 4½ stars on a 5-star scale.

"In general, foods are getting somewhat healthier, but the consumer has to go in with open eyes," says Platkin, whose DietDetective.com website provides health information. "Like airline tickets, airline food is becoming more complicated."

In 2000, when full meals at no extra charge were the industry norm, Platkin released a similar study that showed many airline meals were unhealthy.

After the Sept. 11 terrorist attacks, airlines began cutting costs by eliminating meals.

Many carriers have since re-introduced food service and charge for it.

In Platkin's newly released analysis, he assigns each airline a score based on the variety of food, nutritional value, calorie count and the airlines' willingness to provide nutritional information.

The airlines' scores reflects their full range of in-flight food offerings.

Snack choices fall into a wide range

All airlines offer coach passengers nuts or another snack item for free. Some airlines also sell snack boxes or meals, usually depending on flight length.