Your airline seat may not have much padding, but the airline's schedule sure does.

Delta Air Lines Flight 715 from New York to Los Angeles now takes more than seven hours to fly across the country, according to the airline's March schedule. That's an hour longer than the same flight in the same type of aircraft took in 1996. A Phoenix-Las Vegas flight at Southwest Airlines that used to be scheduled at 60 minutes now gets 80 minutes. What was once a two-hour American Airlines trip from Chicago to Newark, N.J., now is two-and-a-half hours, according to the airline's schedule.

Across the airline industry, carriers have been adding minutes to "block times"—the scheduled durations—baking delays into trips so that late flights officially arrive "on-time" and operations run better because flights pull into gates more often on schedule. Even though the recession has led airlines to cut flights and reduce congestion at many airports and in the skies, the move to pump up schedules has continued: Last year, most airlines added padding to scores of flights.

For some airlines, longer scheduled times for flights reflects the reality of inefficiency in the nation's air travel system, which often can't handle the volume of planes without delay, especially when bad weather hits. For others, lengthening scheduled arrival times boosts on-time rankings charted by the Department of Transportation: Those numbers can have a real effect on public perception. And in some cases, block times have grown simply because airlines have been making so many schedule changes as they have reduced capacity over the past two years. Flights that took off without a wait can now end up stuck waiting behind a line of jets because departure times have been changed.

For travelers, it can seem like airlines are cheating. "If you leave late, you know you will arrive late. But now you leave late and arrive early," said frequent traveler Steve Edmonds, who works for the city of Austin, Texas.