Do you like watching a movie or a favorite TV show during a long flight? Be prepared to watch on your tiny smartphone screen if you don't remember to pack a tablet.

Three of the largest U.S. airlines are removing seatback screens from most narrowbody aircraft in their domestic fleets, as reported last week by Bloomberg. American Airlines, United Airlines, and Alaska Air are all removing screens from medium-range Boeing 737 and Airbus A320 aircraft.

There are a few exceptions and for now passengers will encounter a mixed bag as airlines shift from seatbacks to streaming. American and United will keep seatback screens on some cross-country flights between New York and Los Angeles or San Francisco. United is also retaining screens in Boeing 737s that it acquired in the merger with Continental in 2010, and offering free live DirecTV service.

Depending on which airline you fly, you may have already capitulated to B.Y.O.S. - where the S now stands for screen instead of snacks. Southwest Airlines has never equipped its Boeing 737s with seatback screens and has no plans to start.

On the other side of the aisle, so to speak, Delta and JetBlue are sticking with on-demand seatback entertainment, at least for now.

That may prove to be a wise choice. As noted in the most recent J.D. Power airline satisfaction study, released last May, "Specific in-flight amenities that have the greatest positive effect on customer satisfaction are fresh food, seatback games and seatback live television." In-flight services continues to be the lowest-ranked factor in the study, as many airlines still struggle with in-flight entertainment, connectivity and in-seat power, said Michael Taylor, travel intelligence lead at J.D. Power.

Yet the trendline is undeniable. Now that most travelers carry electronic devices, fewer airlines around the world have seatback screens. Taking the screens out of seats makes smart money sense on a number of fronts: carriers don't have to buy or maintain the hardware; planes are lighter and more fuel efficient; and seats can be made thinner, the better to cram in another row or two.

Travelers who are upset to see seatbeack screens go by the wayside might find solace in faster Wi-Fi and seatside power outlets.

Earlier this year, American Airlines installed satellite connectivity on its entire fleet of domestic narrowbodies and now offers no-buffering, high-speed Wi-Fi and live TV on more aircraft than any other airline. Better yet, the carrier is installing USB power outlets and tablet holders at every seat across its mainline fleet.

And last year, Delta Air Lines CEO Ed Bastian told Barron's, "Our goal is to make Wi-Fi free with high-speed quality. It will take another year or two to make that happen."

As passengers are forced to be more self-reliant when it comes to in-flight entertainment, just remember that it never hurts to pack a good book, just in case.