What makes an air travel terrible? Long lines, delays, or bad airplane food? A recent survey showed that airlines have a long way to go in making their meals and snacks nutritious and low in calories, according to a CNN report.

Charles Platkin, nutrition professor at Hunter College and City University of New York, said: "I don't think airlines are keeping up with the trends across the United States, the 'better for you' food trend, the organic trend."

After surveying 12 major U.S. air carriers and ranking them according to 10 criteria, including whether they include low-calorie, nutritious items on their menus, Platkin found most airlines are also failing to provide nutritional information about their menu items that would allow passengers to make the healthiest choices.

He focused on meals and snacks available for economy-class passengers on domestic flights. The results of his survey were posted in November on dietdetective.com, a website that Platkin runs.

In the time since Platkin began conducting his surveys in 2000, airlines have gone from providing free meals, to selling snacks in supersized portions, to now selling meals and smaller portions of snacks.

Even with smaller snack portions, too many of the options are still high in calories, according to Platkin's survey. The meal choices seem better than the snacks; at least some of them are low-calorie for some airlines.

Of course, healthy food is not just about keeping the calorie count in check. Platkin and his colleagues also took into account protein, fat and sugar, using nutritional information from the airline if it was provided, or estimating in cases where they got only recipes from the airline.

The improvements that airlines have made so far, mostly in providing healthier meals, will probably continue as customers become more interested in what they are eating and put pressure on airlines to tell them, Platkin said.

As large chain restaurants start to post calorie information on their menus, which the Affordable Care Act will require them to do by the end of 2016, people will start to expect the same on airlines, Platkin said.