Airline service in key areas such as on-time performance and baggage handling has improved in recent years, as congestion moderated amid a decline in travel, according to researchers.

The improvement comes after airline performance reached a low point in 2007, according to a 20-year overview of the Airline Quality Rating, an annual study of airline performance. The study’s airline rankings for 2010 will be announced today.

Ratings for the airline industry as a whole in 2010 improved in three of the four categories in the study, according to partial findings released ahead of the rankings. On-time performance rose to 80 percent from 79.4 percent in 2009; the rate of mishandled baggage ticked down to 3.49 per 1,000 passengers from 3.88 a year earlier; and the rate of bumpings off overbooked flights fell to 1.08 per 10,000 passengers from 1.19 in 2009.

However, customer complaints to the government increased. That’s because flight disruptions tend to disrupt travelers’ lives a lot more than they used to, said Dean Headley, an associate professor of marketing at Wichita State and co-author of the Airline Quality Rating.

While in the past a cancellation meant catching the next flight out, airlines now have cut flight schedules and planes are more full.

As a result, fliers “may have to wait two or three flights or until the next day before they can fulfill their travel plans,” Headley said.

Airline performance was relatively stable during the 1990s, Headley said. But in 1999 and 2000, airlines added to their flight schedules amid strong travel demand, and the increased congestion led to declines in performance. The roller coaster economy in the following years led to volatile airline performance as well.

An update of the national air traffic control infrastructure could ease problems from heavy flight traffic in future years, Headley said.