Delta Air Lines will stop charging for its in-flight entertainment system, a rare reversal of fees in air travel.

Movies, TV shows and music will be available for free starting July 1 on any two-class airplane, or about 90 percent of its fleet, Delta said.

Its onboard entertainment package, called Delta Studio, varies in breadth from plane to plane, but the full suite includes about 400 movies (100 from other countries), 750 television shows, 2,400 songs, 18 live satellite TV channels and video games.

Delta says it operates the largest entertainment-equipped fleet in the world, with more than 1,000 aircraft outfitted with Wi-Fi technology and 400 aircraft with seat-back screens and entertainment software.

By investing in new seat-back systems, Delta is straying from industry trends. Many U.S. airlines have done away with, or significantly downsized, seat-back systems, citing consumers' use of personal devices. The screens add weight and airlines save money on fuel by removing the monitors.

"The only thing better than operating the world's largest in-flight entertainment-equipped fleet is providing it free to all our guests," Tim Mapes, Delta's senior vice president of marketing, said in a statement. "Our commitment is to provide Delta customers with the industry's best onboard services — period."

The airline has gradually unveiled upgrades aimed at improving the onboard experience. Delta has modernized the interior on hundreds of planes, including bigger overhead bins, better screens, ambient (or mood-like) LED lighting, new bathrooms and new seats with power outlets.

Delta is working through a multiyear retirement plan for all of its nearly 200 narrow-body MD-88 and MD-90 aircraft, which are some of the oldest operating commercial jets in the U.S.

Delta recently announced it ordered 37 new Airbus A321s, bringing the total order for that aircraft to 82. These, along with the 40 Boeing 737-900ERs on order, are part of the replacement plans for those older planes, which are frequently flown into and out of Minneapolis-St. Paul International Airport.

The photo at top is of Delta's 321 interior seatback entertainment device.

Kristen Leigh Painter • 612-673-4767